Adaptive value

Vertical migrations are performed by so great a range of species that this behaviour must presumably be an adaptation of major importance, but the benefits are not altogether clear. Many of these migrating forms are herbivores grazing on the phytoplankton, and we may wonder what advantage it is to them to spend so much time away from the surface layers where they find their food. Different species must gain different advantages, and some of the possible benefits are as follows (e) Control of...

Aerial and satellite surveys

Since the late 1970s, reasonably accurate remote sensing of the oceans from aircraft and satellites has been possible. Remote sensing depends on sensors mounted in the aircraft or satellite, picking up naturally occurring electromagnetic radiation, or generating electromagnetic energy and measuring it after reflection from the sea. The advantage of these new systems is that large areas can be surveyed at one time. Considerable skill goes into the design of the sensors and the interpretation of...

Age determination

In many species, age can be determined by examining the periodic markings on meristic structures such as scales, otoliths and opercular bones. The best structure to use varies between species (see Table 9.1). There are many difficulties of interpretation of these markings, and they tend to become less reliable as the age of a fish increases, but the method is useful and widely applied. The age groups of fish are commonly designated as follows Group 0 Fish of less than one complete year of life....

Beach protection and cleaning

There is no doubt that in the case of oil spills, the old adage 'prevention is better than cure' has never been truer. However, with ever increasing oil exploration and distribution, the opportunities for spills are now greater than ever. Many spills result from human error and from severe weather conditions. However, economic factors also come into play. There is no doubt that in the case of tanker spills, many could be prevented if all tankers were built with double hulls. Several incidences...

Biological features of the marine environment

Seawater is evidently an excellent medium for an abundance and variety of life. We know from geological findings that the seas have been well populated since the earliest time for which we have fossil records. It is widely thought that life originated in the sea, most likely in pools on the seashore where many different solutions of varying composition and concentration could accumulate in various conditions of temperature and illumination. Alternatively, some scientists are now postulating...

Coastal zone management

Marine And Coastal Ecology

At the present time, and partly because of the difficulties experienced with marine site protection, more emphasis is being placed on management of the marine environment as a whole. Protected sites are more likely to achieve their aims if Figure 10.4 Lundy Marine Nature Reserve zoning scheme. The map distributed to reserve users is in colour which makes interpretation quick and easy. (By kind permission of English Nature. Map based on Admiralty Chart 1164 with the permission of the controller...

Coral reefs

Coral reefs have always fascinated man. Their richness and diversity have provided a livelihood for coastal communities for thousands of years. Now their spectacularly colourful beauty can be seen by millions through television and increasing numbers of tourists visit reefs to scuba dive, snorkel or view the reef from glass bottomed boats. The major part of most coral reefs lies below the low tide mark since corals are killed by prolonged exposure to air. So the coral reef is not truly a...

Crustaceans and seaweeds

Prawns and shrimps are the most widely cultivated crustaceans and are reared mainly in the warmer parts of the world using pond culture techniques. Prawn culture in Asia currently accounts for three-quarters of world production. The giant tiger prawn (Penaeus monodon) which weighs up to 500 g is reared in intensive systems both for the markets and as a valuable export commodity. Most large supermarket chains in the UK have this species on sale. Lobsters and crabs are also reared in captivity...

Deepscattering layers

Early studies of these diel vertical movements of plankton and other creatures were mainly confined to populations of shallow water, but during World War II it became apparent that this phenomenon is of very wide occurrence throughout the deep oceans. Physicists investigating the use of underwater echoes for the location of submarines obtained records during daylight hours of a sound-reflecting layer in the deep water beyond the continental shelf (Dietz, 1962 Farquhar, 1977). On echogram...

Deepsea food supply

Whereas in shallow water much of the food supply of the sea bottom comes directly from the surface layers, in very deep water it is unlikely that much surface plankton reaches the bottom intact because most of it is consumed by pelagic Table 6.2 Percentages of Dry Weight Biomass Contributed by Different Animal Groups in Macrobenthos of Western English Channel. Polychaetes and Nemertines 25.79 organisms on the way down. Between the productive surface layers and the deeper parts of the ocean...

Depth measurements

The classical method of measuring the depth of the sea was by means of sounding weights and lines. The weight was lowered from the vessel until it struck bottom and the length of line measured, usually by means of a meter attached to a sheave through which the line passed. This method has been superseded by sonic sounding. Sonar stands for 'sound and ranging' and is the detection of objects under water using sound. There are many applications including depth measurement, seabed profiling and...

Difficulties with fishery policies

The CFP faces a great many difficulties and is by no means a fully effective system. Disputes between member states are common and at times can even lead to violence. Politicians and scientists are often in disagreement particularly concerning TACs and such aspects as discards and bycatch. Nevertheless, despite these difficulties a degree of accord has been reached on aspects such as minimum mesh and landing sizes, closed areas and seasons for certain fisheries, and regulations on size and use...

Drift bottles

The major surface currents of the oceans became known during the days of sailing ships when this knowledge was needed for successful ocean voyages. Information was accumulated by noting the course of drifting objects such as becalmed ships, drift-wood or pieces of wreckage. Oceanographers refined this technique by using specially designed drift bottles. These provided much of the original information about water movements around the British Isles. They are hardly ever used now but are described...

Effects of raw or undertreated sewage dumping

The addition of sewage to water can greatly increase fertility by release of nutrients, with possible long-term beneficial effects. However, in most cases the effects are detrimental because of the sheer volume of the discharges. Such effects include foul deposits, deoxygenation, eutrophication, reduced salinity, infection and toxic residues. Discharge of untreated sewage may result in strandings of recognizable faecal material and other objectionable objects. Unless fully treated, solid...

Excursions

The educational value of a marine ecology course is enhanced by any of the following expeditions A Visit to an estuary to observe the distribution of freshwater, estuarine and marine species. Where possible, methods are devised for measuring water depths and collecting water samples from the surface, middle depths and bottom at several stations along the estuary at intervals through the tidal cycle. Salinities, temperatures and oxygen contents are measured. On diagrammatic sections of the...

Fishery research

Many interrelated fields of study are included under the general heading of fishery research, including investigations of the distribution and natural history of fish, the size and composition of stocks, and the extent and causes of fluctuations in stocks. One of the chief objectives of this science is to achieve sufficient understanding of the factors influencing fish stocks to be able to predict reliably the long-term effects, on the quantities of fish caught, of varying the methods and...

Foodfish production

Suspension, surface deposit and sediment feeding animals of the sea bottom are preyed upon by a variety of carnivores, including many of the food fish highly prized by man. Studies of biomass and composition of benthic communities therefore give some indication of the extent to which areas can support stocks of fish. The production of animal material on the sea floor can be regarded as 'useful' or 'wasteful' according to whether it contributes to the formation of commercially valuable species...

Illumination

Compared to the depth of the ocean, light does not reach very far into the sea. Illumination of the surface layers varies with place, time and conditions depending upon the intensity of light penetrating the surface and upon the transparency of the water. The strength of the incident light varies diurnally, seasonally and with latitude, and is influenced by cloud conditions and atmospheric absorption. Much of the incident light is reflected from the surface, more light being reflected from a...

Indirect effects

One of the problems with all types of fishing gear is that it always has an incidental or by-catch of non-target species. This may include other commercial and noncommercial fish, seabirds and marine mammals. Drift or gill nets are of particular concern in this respect. Modern drift nets may extend for several kilometres and are made from monofilament nylon. This makes them virtually invisible to animals using sonar. High seas drift netting was banned in December 1992 by a United Nations...

Introduction

Ecology is the study of relationships between organisms and their surroundings. This study is fundamental to an understanding of biology because organisms cannot live as isolated units. The activities which comprise their lives are dependent upon, and closely controlled by, their external circumstances, by the physical and chemical conditions in which they live and the populations of other organisms with which they interact. In addition, the activities of organisms have effects on their...

Nitrate and phosphate

Nitrogen in combined form is present in seawater as nitrate, nitrite, ammonium ions and traces of nitrogen-containing organic compounds. Nitrate ions predominate, but in the uppermost 100 m and also close to the bottom there are sometimes appreciable amounts of ammonium and nitrite formed by biological activity. Phosphorus is present almost entirely as orthophosphate ions H2POzT and HPO42 with traces of organic phosphorus. The concentrations of these combined forms of nitrogen and phosphorus...

Ocean seasons

Seasonal Variations Sea With Diagram

Seasonal variations in temperature, illumination and availability of nutrients in the surface layers of the sea impose a pronounced seasonal cycle in production and composition of the plankton between winter and summer, particularly in temperate latitudes (Figure 5.11). Both geographical and year-to-year patterns of fluctuation have their origins within the dynamics of the seasonal cycle. For example, continuous plankton recorder studies have shown that the copepod Centropages hamatus in the...

Position fixing

Whatever the method used to obtain a biological sample from the sea-bed, it is important to know exactly where the sample came from. Most modern research vessels are equipped with Decca Navigator or Loran C systems which utilize Figure 3.34 Towed camera sled used by A.J. Southward at MBA, Plymouth. Reproduced from Gage and Tyler (1991) from photographs and drawings in Southward et al. (1976). Figure 3.34 Towed camera sled used by A.J. Southward at MBA, Plymouth. Reproduced from Gage and Tyler...

Protected marine areas and legislation in the UK

On land the concept of protecting and conserving areas considered to be of prime importance, in terms of the wildlife and habitats they contain, is well established. The first National Nature Reserve was declared in the UK in 1951 and there are now over 200 with 43 that are over 1000 ha in size (IUCN, 1994). In contrast, as of 1996, there are only two statutory Marine Nature Reserves, Lundy Island in the Bristol Channel and Skomer Island off the Pembrokeshire coast. These were declared in 1986...

References and further reading

LeB (1971). Heterotrophic utilization of dissolved organic compounds in the sea. III. Measurements of the oxidation rates and concentrations of glucose and amino acids in sea water. J. Mar. Biol. Assoc. UK., 51, 111-25. Bainbridge, R. (1953). Studies of the Interrelationships of Zooplankton and Phytoplankton. J. Mar. Biol. Ass. UK, 32, 385. Bainbridge, R. (1957). The Size, Shape and Density of Marine Phytoplankton Concentrations. Biol. Rev., 32, 91. Boalch, G.T.,...

Sewage treatment

Sewage enters the sea via short and long sea outfalls, stormwater drains and rivers. The discharge of raw sewage into coastal waters is still widespread in the UK and in many other countries. In Europe, increasing efforts are being made to treat sewage effectively before discharge. This clearly reduces the impact of the sewage both on the marine environment and on coastal amenities. Sewage pollution of coastal and estuarine waters is usually most severe during the summer when temperatures are...

Some mathematical models

The aim of ecological studies is to achieve sufficient understanding of the interactions between organisms and their environments to be able to express these Figure 5.16 Kelp (Laminaria hyperborea) in (a) spring and summer the old frond is discarded as the new frond grows and (b) in winter. (c) The tunicate Diazona violacea in winter only a hard bud remains and (d) in summer. Figure 5.16 Kelp (Laminaria hyperborea) in (a) spring and summer the old frond is discarded as the new frond grows and...

Specific gravity and pressure

The specific gravity of seawater varies with temperature and salinity and very slightly with pressure. At 20oC and atmospheric pressure, seawater of salinity 35 o has a specific gravity of 1.026. At salinities above 24.7 o the temperature of maximum density lies below the freezing point. Because of this, cooling of the sea's surface to freezing point does not produce a surface layer of light water, as it does in fresh water where the temperature of maximum density is 40C. In contrast to fresh...

Stock growth

Grp Marine Growth

The growth potential of the stock may be estimated from data on the composition of the stock and the mean growth rates of each age group, due allowance being made for differences of growth rate of the two sexes and in different areas over which the stock is distributed. Figure 9.34 North Sea haddock recruitment, 1960-1990. (From Shepherd, J.G. 1990. 'Stability and the objectives of fisheries management the scientific background. Lab. Leafl., MAFF Direct. Fish. Res., Lowestoft (64), Crown...

Subsurface drifters

Oceanographic Drogue

It is possible to detect and measure water movements at middle depths by using neutrally buoyant floats, the weight of which can be accurately adjusted to match the density of the water so that they sink to a predetermined depth and then drift Figure 3.1 An ARGOS satellite-tracked drifting buoy and its drogue. Figure 3.1 An ARGOS satellite-tracked drifting buoy and its drogue. with the current. Such floats are tracked acoustically or by satellite and are used extensively for open ocean studies....

The continental shelf

Close to land the sea is mostly shallow, the bottom shelving gradually from the shore to a depth of about 200 m. This coastal ledge of shallow sea bottom is the continental shelf (see Figure 1.2). About 8 per cent of the total sea area lies above it. Its seaward margin is termed the continental edge, beyond which the water becomes much deeper. The steeper gradient beyond the continental edge is termed the continental slope. The width of the continental shelf varies very much in different parts...

The food supply

The food supply of the benthic macrofauna derives, directly or indirectly, almost entirely from living and dead particulate matter sinking from the overlying water. There is very little primary production of food on the sea-bed because plants can grow only where there is sufficient light for photosynthesis. Vegetation on the sea bottom is therefore limited to shallow water. Large algae produce a lush growth on and near the shore, especially in middle latitudes, and form a primary food source...

The grazing rate

Although the interactions between plant and animal populations are difficult to elucidate, the grazing rate of the herbivorous zooplankton is certainly one of the factors which regulates the size of the standing stock of phytoplankton, and therefore influences the production rate. The quantity of epipelagic zooplankton generally correlates more closely with the quantity of plant nutrients in the surface layer than with the size of stock of phytoplankton, indicating how greatly grazing reduces...

The role of carbon dioxide

Carbon dioxide is stored in the atmosphere, the land and in the oceans. The latter have an immense capacity to contain CO2, storing by far the largest amount and thus having a major controlling influence on atmospheric CO2 levels. Physical, biological and chemical factors are all involved in the uptake of CO2 by the oceans. Dissolved CO2 in its several forms is conveyed between surface and deeper levels by currents and water-mixing processes. However, phytoplankton plays the leading role in CO2...

Topics for further study and class discussion or written work

1 Describe in outline the main ocean currents, at the surface and below. How are they set in motion and what factors influence their courses In what ways is this knowledge of interest to biologists 2 In general terms describe the overall conditions of life in the marine environment. Giving your reasons, what do you consider to be the major subdivisions of the environment In what respects do biological conditions in the sea differ from those of freshwater environments 3 What are the chief...

Toxic heavy metals

Many heavy metals such as arsenic, lead, cadmium, mercury and copper are naturally present in seawater at very low concentrations reflecting their low solubility (see Table 4.3). Various organisms need some of these in very small amounts, for normal metabolism. However, increased concentrations resulting from pollution may be harmful both to marine organisms and to humans. The concentration of heavy metals in the water may be raised locally by discharges from many industrial processes, and in...

Underwater observations

It would simplify many problems in marine biology if the range of direct observation could be extended. The only marine populations which are easily accessible to close inspection are those of the seashore, and then only for a part of each tidal cycle. Our knowledge of the rest of marine life comes almost entirely from the incomplete samples obtained by nets, dredges, grabs and similar devices. Recently, new techniques for visual underwater exploration have been developed, and have already...

Water movements below the surface

Oceanic circulation should be visualized in three dimensions. We have already mentioned that wind action on the surface sets different layers of water in movement in different directions. Where the wind causes a surface current, the moving water must be replaced by a corresponding inflow from elsewhere. This may be surface water from other regions or deep water rising to the surface, often both. Also, when surface water flows from low to high latitudes, cooling leads eventually to sinking and...

Waves

Breaking And Entering Diagram

The commonest cause of surface waves is the action of wind on the surface transmitting energy to the water and setting it in orbital motion (Figure 8.4). The size of waves depends upon the speed of the wind, the length of time during which it blows and the uninterrupted distance over which the wind acts on the water (the fetch). Surface waves do not mix the water to any great depth. Their motion falls off sharply with depth, and at a depth equal to half the wavelength of the waves the water is...

ATP measurements

A source of inaccuracy in many methods of estimating biomass is the difficulty of distinguishing living from non-living tissue. In samples containing appreciable amounts of non-living organic matter there are possibilities of greater accuracy from biomass estimates based on measurements of the adenosine triphosphate ATP content, as this is a constituent of all live protoplasm but is virtually absent from dead cells. The technique measures the amount of light emitted when ATP is added to an...

Biological factors affecting distribution of communities

Although inorganic factors exert a major control, there are also biological factors which influence the distribution and composition of benthic communities. The physical and chemical features of the environment determine a range of species which compete, but success or failure in a particular habitat depends ultimately on qualities inherent in the organisms themselves. For example, they are able to some extent to choose their position. Free-living forms can move about to find areas that suit...

Other senses

Gigantactis

The ears and lateral line organs of fish are sensitive to vibrations in the water, and enable fish to detect and locate objects in their vicinity. Many species have very acute hearing, and in some deep-level fish the lateral line system is very well developed, for example, in myctophids and macrourids, and this must compensate Figure 4.12 Some bathypelagic fishes showing various adaptations for life in darkness. a Argyropelecus - photophores and tubular eyes. b Linophryne - luminous lure and...

Primary production

Producers Ecology

The synthesis of organic compounds from the inorganic constituents of seawater by the activity of organisms is termed production. It is effected almost entirely by the photosynthetic activity of marine plants. The raw materials are water H2O , carbon dioxide CO2 and various other substances known as nutrients. The latter are mainly inorganic ions, principally nitrate and phosphate. Chlorophyll-containing plants, by making use of light energy, are able to combine these simple substances to...

Bioluminescence

Stomiatoid Fish

The marine fauna includes a wide variety of bioluminescent species, with numerous examples known in almost all the major groups Boden and Kampa, 1964 Herring, 1978 Tett and Kelly, 1973 . Although the most numerous bioluminescent organisms are very small, chiefly dinoflagellates, the phenomenon is also commonly exhibited by many larger animals, especially fish, crustacea and cephalopods living in the mesopelagic zone. The common occurrence of bioluminescence in the sea, in contrast to its rarity...

Plankton indicators

Salpa Fusiformis

Because different communities of organisms are found in different parts of the sea, it is possible to distinguish particular bodies of water not only by their physical and chemical features, but also to some extent by their characteristic populations. Moving water carries with it an assortment of planktonts which can be regarded as natural drift bottles, and by observing the distribution and intermingling of different planktonic populations it may sometimes be possible to trace the movement and...

Water samples and temperaturesalinity measurements

Hydrography Instrument

Water samples from different depths are often required both by physical oceanographers and by biological oceanographers. Information from the analysis of such samples, along with temperature and salinity measurements, not only provides direct information about a water body, but has also been used to obtain indirect measurements of deep water circulation. Such ocean currents are difficult to measure directly, especially the slow movements of water at deep levels. The waters of different parts of...

Age census

Stock samples are examined to determine the number of fish in each age group. Where annual markings are absent, unreadable or of doubtful reliability, Petersen's method of age analysis is used. Measurements are made of the length of each fish in representative samples of stock, and length frequency graphs are plotted. These polymodal curves can be broken down to their separate modes, each representing an age group within the sample Figure 9.32 . The age assigned to each mode of the curve can be...

Human impact on the marine environment

Only a hundred years or so ago, it would have seemed inconceivable that anything we did could significantly affect the vast resources of the oceans or result in large-scale alterations and damage to marine ecosystems. We have already seen in Chapter 9 that this is no longer true for fishery resources. Modern technology has resulted in a huge increase in our ability to catch and store edible marine species. Many or most important fishery stocks are now being exploited at levels considered to be...

Major constituents and salinity

Major Ions Seawater

It is uncertain to what extent the composition of seawater may have changed during geological time, but it is not thought to have varied very widely over the period that life has existed. At present, the principal cations are sodium, magnesium, calcium, potassium and strontium, and the chief anions are chloride, sulphate, bromide and bicarbonate. These make up over 99.9 per cent of the dissolved material, forming approximately a 3.5 per cent solution. The amount of inorganic material dissolved...

Chief routes of entry of marine pollutants

Marine pollutants find their way into the sea not only through deliberate routes such as sewage discharges and dumping legal and illegal but also by a variety of other, not always obvious, routes outlined below. Many pollutants reach the sea either through direct drainage from coastal towns and industries or indirectly via rivers. Dilute industrial effluents, treated sewage and cooling water are often discharged into rivers and estuaries. Fertilizers, pesticides and animal wastes may drain into...

Physical factors affecting distribution of communities

We have already outlined in Chapter 4 the major hydrographic parameters which control the distribution of marine organisms - the temperature of the water, its composition, movements, pressure and illumination. Except on the shore and in shallow water, these vary less at the bottom than they do in the upper levels of water. They are none the less important in relation to the distribution of benthic populations, restricting certain species to particular localities and often having a major effect...

Cod Gadus morhua

North Sea And British Isles Fish Stocks

No other single species has been of such importance as cod for human consumption. Many millions are still taken each year although there is now growing concern over the state of many stocks. For example the Canadian Grand Banks cod fishery in the NW Atlantic finally collapsed by 1992. Cod are mainly caught by trawl, and some are also captured by long line. The cod Figure 9.11 has an extensive range over the continental shelf and slope to a depth of about 600 m throughout the Arctic and the...

Seasonal changes in plankton around the British Isles

Marine Ecology

Eggs, larvae and spores of benthic plants and animals are often a conspicuous part of the plankton of neritic water, and some of the most obvious seasonal changes are related to the reproductive seasons of the benthos. We can summarize certain seasonal features of the plankton of shallow water around the British Isles as follows Boalch et al., 1978 Figures 5.12-5.15 . Surface cooling is continuous during the winter, reaching a minimum temperature throughout the water column, usually in early...

Standing stock measurements

The earliest attempts to measure organic production in the sea were indirect, being based on estimates of the total amount of plant material in the water, i.e. the standing stock. This does not give a direct indication of the rate of production because account must be taken of the rate of turnover. If the plants are being very rapidly eaten, high production may maintain only a small standing stock. For example, on a well-lit coral reef, as much as 1-5 kg of seaweed can grow on every square...

The microbial loop

Microbial Loop Nutrient

In the marine ecosystem the foregoing elementary account of the organic food cycle must be extended to take account of the significance of dissolved organic matter DOM in seawater. As mentioned earlier see Section 4.3.3 an appreciable proportion of the products of photosynthesis become released from plant cells and soon appear in the water as DOM. Although some of this component of primary production may be reabsorbed by phytoplankton, much of it is rapidly taken up by planktonic bacteria. The...

Dissolved organic matter DOM

Particulate organic matter is always present in seawater, but in addition, varying quantities of organic compounds are present in solution. This is referred to as dissolved organic matter DOM or dissolved organic carbon DOC Jorgensen, 1976 Williams, 1975 . The estimation of minute quantities of organic solutes is difficult, but it appears that ocean water commonly contains about 2 mg carbon per litre in dissolved organic forms, in some of which nitrogen, phosphorus, sulphur, iron or cobalt are...

Lampitt Snow Falls In The Ocean

Settlement of Mytilus. J. Anim. Ecol., 33, 513-23. Bayne, B.L. 1969 . The Gregarious behaviour of the larvae of Ostrea edulis at settlement. J. Mar. Btol. Ass. UK, 49, 327. Buchanan, J.B. et al. 1978 . Variability in benthic macrofauna. J. Mar. Biol. Ass. UK, 58, 191-209. Corliss, J.B. and Ballard, R.D. 1977 . Oases of life in the cold abyss. National Geographic Magazine, 152, 441-53. Crisp, D.J. 1974 . Factors influencing the settlement of marine invertebrate larvae. In...

Pelagic deposits

Globigerina Ooze

Pelagic deposits occur beneath deep water beyond the edge of the continental slope, carpeting the deep ocean basins. Much of this material is of fine texture, and its nature varies with the depth and with the types of organisms that abound in the overlying water. At depths of less than about 6000 m, pelagic deposits contain a considerable proportion of material of biological origin, commonly some 30 per cent or more by weight. Although these deposits are termed 'organic', they seldom contain...

Keeping the catch

Cod Fishing Vessels

Keeping the catch fresh once the fish have been caught has always been a problem and the length of time iced fish will remain in reasonable condition effectively limits the duration of fishing for distant-water trawlers if they rely solely on ice for preservation. The development in recent years of efficient and cost-effective refrigeration and storage systems on board larger fishing boats, has made much longer fishing trips possible. If fish are stored directly in the hold, then dry...

Surface currents

Surface Currents Trade Winds

The chief surface currents and their relation to prevailing winds are shown in Figure 1.6. In the Equatorial belt between the Tropics of Cancer and Capricorn, the North-East and South-East Trade Winds blow fairly consistently throughout the year, setting in motion the surface water to form the great North and South Equatorial Currents which flow from east to west in the Atlantic, Indian and Pacific Oceans. Across the path of these currents lie continents which deflect the water north or south....

Behavioural and activity responses of mobile animals

Physiological and behavioural adaptations are necessary to withstand the fluctuating nature of the shore environment Gibson, 1969 . The wide and rapid changes of temperature and salinity that occur on the shore surface during low tide require wide eurythermy and euryhalinity in the exposed population Cornelius, 1972 Southward, 1958 . They must also be capable of making appropriate adjustments of behaviour in response to changes in their surroundings. The limpet Patella , if wetted with...

Global primary production

Primary Production Per Year

In Table 5.1, comparisons are made between primary production on the land and in the sea. The concept that open ocean areas have a productivity comparable to that of deserts on the land and much lower than that of coastal areas and upwelling zones, is well established. However, techniques for measuring organic production are constantly being refined and some recent data suggest that there may be two to three times as much organic matter per unit of surface area in the open ocean than previously...

Diel patterns

The study of SSLs together with data from deep-level net samples indicate that throughout the oceans, in both deep and shallow water, a numerous and varied assortment of animals perform vertical migrations with a diel rhythm. There are differences in the depths through which different species move, the speeds at which they ascend and descend, and the precise times at which they make their movements, and the same species may behave differently in different areas and at different times, but there...

Some laboratory exercises

A Salinity measurements by titration and conductimetry. B pH measurements in seawater and determination of titration alkalinity. C Estimation of a minor constituent for example phosphate Murphy and Riley, 1962 . D Elementary studies on barnacles, for example Semibalanus balanoides, B. perforatus, B. crenatus, Chthamalus stellatus, Elminius modestus. Diagnostic characters. Measurement of rate of cirral activity over ranges of temperature, salinity and pH. Comparison of the activity ranges of...

Fauna and flora

Pelagic organisms in estuaries face difficulties of maintaining position in the ebb and flow of water. The net transport of water is downstream, tending to flush pelagic organisms out to sea. On the rising tide there is some danger that they might be carried up into lethally low salinities. Some pelagic animals or larvae adjust their behaviour to reduce these dangers. Some swim mainly on the flood tide and sink to the bottom on the ebb, thereby avoiding being washed too far seawards, e.g....

Wars and fish stocks

During the first half of the twentieth century the fisheries of the north-east Atlantic were twice interrupted by war. Conditions on some of the major fishing grounds visited by British vessels have fluctuated correspondingly, with symptoms of underfishing during war years and severe overfishing in peacetime. For example, the North Sea provides an important fishery for haddock. During the years prior to 1914, the total landings of haddock from this area showed a fairly steady decline. During...

Terrigenous deposits

Terrigenous deposits are found near land, covering the continental shelf and upper parts of the continental slope. Much of this material is derived from weathering and erosion of exposed land surfaces, and consists largely of particles worn from the coast by wave action or carried into the sea by rivers or glaciers. Terrigenous deposits contain some organic material, often some 0.01-0.5 per cent of the dry weight, the finer-texture deposits usually having the greater proportion of organic...

Energetics of a marine ecosystem

Living organisms, unlike machines, cease to exist once they stop working. All biological activity depends upon continual transfers and transformations of energy, without which any natural living system almost immediately disintegrates irreversibly. We will now draw together some of the information from preceding pages in an elementary consideration of certain energy relationships of marine life, with particular reference to shelf seas around the British Isles. Directly or indirectly the source...

Coriolis effect

Platebounderies

Wind action on the surface does not simply blow the water in the same direction as the wind, except in very shallow depths. The earth's rotation causes a deflecting effect so that surface water is moved at an angle to the wind. This deflection, generally known as the Coriolis effect after the French engineer and mathematician who first derived an equation for it, influences any object moving on the earth's surface, and is due to the rotational movement of the earth beneath the moving body. In...

European hake Merluccius merluccius

Plaice Nursery Norway

Hake Figure 9.15 extend along the eastern side of the Atlantic from Norway and Iceland where it is only seasonally common to Morocco in North Africa. Hake are also found in the Mediterranean. It is a fish of deep water, occurring mainly at depths below 200 m, but throughout adult life it performs seasonal migrations into shallower water for spawning during spring and summer, returning to deep water in the autumn. Further south, along African and American coasts, extending down to South Africa...

Amphidromic Point North

North Sea Tide Tidal Lines

Although the behaviour of tides is very complex, the underlying cause of their motion has been understood since Newton 1647-1727 accounted for tides as due to the gravitational attraction of the moon and the sun upon the oceans. A brief description is given here but fuller explanations can be found in the Admiralty Manual of Tides Doodson and Warburg, 1941, reprinted 1973 . Other useful and practical material on tides and tidal streams can be found in the RYA Manual of Navigation RYA, 1981 ....

Plate tectonics

Destructive Margins

The theory of plate tectonics was formulated in the late 1960s and brings together the theories of sea floor spreading and continental drift. The continents and ocean basins are believed to have evolved over the past 200 million years or so and plate tectonics provides an explanation for the way in which this may have happened. According to current theories of plate tectonics and sea floor spreading, the outer crust of the earth the lithosphere is made up of about 20 separate lithospheric...

Deepsea hydrothermal vent communities

Deep Sea Food Webs

In some areas of the eastern Pacific and Atlantic, hot springs or hydrothermal vents escape from volcanic fissures along the global system of mid-oceanic ridges see Section 1.2.3 where sea-floor spreading occurs. Here water emerges from cracks and crevices at temperatures of up to 250 C. Even hotter vents exist where the water flows at up to 380 C from 'black smoker chimneys', formed from precipitated minerals. In 1977, the manned submersible 'Alvin' explored one of these newly discovered...

Red tides

Certain species of dinoflagellates contain highly toxic substances which can cause the death of other marine creatures which eat them. Under certain conditions when an excess of nutrients is present and the sea is very calm, certain dinoflagellates multiply very rapidly and form a bloom. The water is often discoloured hence the name 'red tide'. Not all 'red tides' are red or toxic, but those that are occasionally cause the death of large numbers of fish. In recent years, many fish farms have...

Oil pollution of beaches

Oil Pollution Sources Sea Diagram

The fate and effects of oil washed up on beaches depend not only on the variables such as oil type, mentioned above, but also on the energy level of the shore degree of exposure to wave energy and on substratum type. In general, the more exposed the shore, the quicker the biological recovery time of the littoral benthos. This applies both to rocky and sedimentary beaches. Oil does not remain long on wave-battered rocky shores, and where vertical cliffs are present the oil may never reach them...

Nutrients

In addition to dissolved carbon dioxide, which is present in seawater in ample quantities to support the most prolific naturally occurring plant growth, there are other substances, the nutrients, which plants also extract from the water and which are essential for their growth. Many of these are minor constituents of seawater, present only in very low concentration, and their supply exerts a dominant control over production. Nitrate and phosphate are of special importance. Where the quantities...

Water bottles

Nansen Reversing Water Bottle

Before the advent of CTD probes and rosette samplers, most water sampling was done using simple water bottles such as the Nansen-Pettersson Figure 3.5 . Most such bottles take the form of an open-ended cylinder with spring-loaded valves for closing the ends. The sampler is lowered with the ends open so that water flows freely through it. When the required depth is reached, a release mechanism is operated by sending a slotted weight known as a messenger down the suspending wire, which causes the...

Elementary classification of the marine environment

Classification Marine Environment

Although the mixing effected by the oceanic circulation ensures that the major parameters vary but little throughout enormous volumes of water, there are nevertheless some strong contrasts between different parts of the sea. The cold, dark, slowly moving bottom layer of the deep ocean is obviously a very different Figure 1.8 Main divisions of the marine environment. Figure 1.8 Main divisions of the marine environment. environment from the well-illuminated, wave-tossed waters of the sea surface,...

Animal life

Subsurface Food Webs

The animal population of sandy shores mainly dwells below the surface, but includes some species which at times emerge to crawl or swim. Along the upper parts of some sandy beaches is a zone where the sand dries out and air penetrates during intervals between periods of submergence. This is the littoral fringe of the sandy shore, which in the British Isles is often inhabited by the burrowing amphipod Talitrus saltator, occurring in great numbers where there is much organic debris deposited...

Radioactive pollution

Radioactive materials may enter the sea from two main sources from weapon testing via atmospheric fallout and from atomic power industries. The main contaminants are strontium-90, caesium-137 and plutonium-239. In the UK, a major source of radiation pollution has been via the discharge of cooling water from Sellafield Nuclear Power Station. The level of discharge has been considerably reduced in recent years but caesium-137 which does not occur naturally remains in sufficient quantities for it...

Chemical composition

Estuary water is not a simple dilution of seawater. Many subtle changes in composition are involved, varying with local conditions. The relative proportions Figure 8.16 Section of Tyne Estuary showing isohalines, isotherms, percentage oxygen saturation and distribution of dominant planktonts at 2 m depth. Zone A - marine plankton containing Sagitta elegans, Nyctiphanes couchi, Calanus, Paracalanus, Pseudo-calanus, nauplii of Semibalanus balanoides, polychaete larvae, etc. Zone B - very sparse...

Mariculture requirements and methods

A primary requirement for animal farming is to keep one's stock within a protected area, where they are safe from predators and can grow under controlled conditions without severe competition for food from unwanted species. Oysters and mussels, once they have settled, remain virtually stationary, and the beds where they are grown can to some extent be protected from enemies and competitors. But fish roam about, often over considerable distances, and fish-pens cannot easily be constructed in the...

Lemon sole Microstomus kitt

Lemon Sole Skin Photos

Like plaice, the lemon sole Figure 9.19 is a flatfish of shelf areas of the north-east Atlantic ranging from the Arctic to the Bay of Biscay. It does not extend as far south as plaice and generally favours a rougher sea bottom, but the two species often occur together. Lemon sole are specially abundant in the north-west part of the North Sea off the east coast of Scotland, also around the Faroes and along the south-west coast of Iceland and these are the most important fishing grounds Figure...

A field course book list

The following books are often useful during field courses General guides Barrett, J.H. and Yonge, C.M. 1972 . Pocket Guide to the Sea-Shore revised edition . London, Collins. Campbell, A.C. and Nicholls, J. 1976 . Hamlyn Guide to the Seashore and Shallow Seas of Britain and Europe. London, Hamlyn. Cremona, J. 1988 . A field atlas of the seashore. Cambridge University Press. Dipper, F.A. and Powell, A. 1984 . A field guide to the water life of Britain. Reader's Digest Nature Lover's Library....

Light and the compensation depth

In the process of photosynthesis the energy of solar radiation becomes fixed as chemical energy in organic compounds. The efficiency of the ocean surface in this energy transformation must vary with locality and conditions, but is probably on average about 0.1-0.5 per cent overall, an efficiency a little lower than that of the land surface. The ability of plants to absorb and utilize light in photochemical reactions is due to their possession of the green pigment chlorophyll and certain other...

Reproductive adaptations

The difficulties of survival on the shore have their effects on all phases of life, including reproductive processes and larval and juvenile stages. The majority of benthic organisms start life as floating or swimming forms in the plankton, and may become widely dispersed in the water before they settle on the sea bottom. Shore creatures face special risks of great losses of pelagic eggs and larvae during this phase if they drift far from the shore and settle outside the zone in which survival...

Buoyancy problems

Buoyancy Problems

Most protoplasm, cell walls, skeletons and shells have a density greater than seawater, and therefore tend to sink. The specific gravity of seawater is usually within the range 1.024-1.028. The overall density of much of the zooplankton is around 1.04 and of fish tissues about 1.07. Within a floating body the distribution of weight determines its orientation in the water. Therefore one of the problems facing pelagic organisms is how to keep afloat in a suitable attitude between whatever levels...

Temperature tolerances and biogeography

Bering Sea Depth Map

Water temperature exerts a major control over the distribution and activities of marine organisms Kinne, 1963 . Temperature tolerances differ widely between species, but each is restricted in distribution within its particular temperature range. Some species can only withstand a very small variation of temperature, and are described as stenothermal. Eurythermal species are those of wide temperature tolerance. Strict stenotherms are chiefly oceanic forms, and their distribution may alter...

Mackerel Scomber scombrus

Mackerel Figure 9.23 are found in warmish water on both sides of the North Atlantic. Their range extends from the south coast of Norway and northern North Sea, along the west coasts of the British Isles and into the English Channel, and as far south as the Canaries. They also occur in the Mediterranean and on the western side of the Atlantic from south Labrador to North Carolina. The life history and migrations of mackerel have been well documented by Lockwood 1976, 1978, 1989 . Two stocks of...

Chemosynthesis

Chemosynthesis Reaction

Some of the bacteria involved in recycling and regeneration are autotrophic. They function as primary producers of organic compounds by reduction of carbon Figure 5.3 Phosphorus cycle in seawater. Figure 5.3 Phosphorus cycle in seawater. Figure 5.4 Nitrogen cycle in seawater. DON is dissolved organic nitrogen. Figure 5.4 Nitrogen cycle in seawater. DON is dissolved organic nitrogen. dioxide in chemosynthetic reactions which parallel the photosynthetic processes of plants, but derive energy from...

Synopses of the British Fauna new series Linnean Society of London and Estuarine and Brackishwater Sciences Association

British Ascidians. No. 2. Graham. A. 1988 . British Prosobranchs 2nd edn No. 3. Naylor, E. 1972 . British Marine Isopods. No. 5. King, P.E. 1974 . British Sea Spiders. 450 Elements of Marine Ecology No. 7. Jones, N.S. 1976 . British Cumaceans. No. 8. Thompson, T.E. 1988 . Molluscs Benthic Opisthobranchs Mollusca Gastropoda 2nd edn . No. 9. Morgan, C.I. and King, P.E. 1976 . British Tardigrades. No. 10. Ryland, J.S. and Hayward, P.J. 1977 . British Anascan Bryozoans....

Urochordata

Siphonophora Zooplankton

There are three planktonic orders the Larvacea, for example Fritillaria, Oikopleura Figure 2.14g Appendicularia the Figure 2.14 Various zooplanktonts from around the British Isles and the groups they represent. a Aglantha digitale Trachymedusa , b Chelophyes appendiculata Siphonophora , c Pleurobrachia pileus Ctenophora , d Sagitta elegans Chaeto-gnatha , e Tomopteris septentrionalis Polychaeta , f Doliolum Dolioletta gegen-bauri Thaliacea , g Oikopleura...

Plankton

Nansen Net Plankton

Detailed methodologies for plankton sampling are given in a variety of texts such as UNESCO 1968 and Omori and Ikeda 1984 . Samples of plankton are usually collected by plankton nets. These are of many designs, but all consist essentially of a long cone of fine-mesh net. The mouth of the net is usually some 50-100 cm in diameter, and is held open by a strong hoop to which the tow-rope is attached by three bridles Figure 3.11 . The narrow end of the net is firmly tied to a small metal or plastic...

References

Behavioural Basis of Intertidal Zonation of Eurydice pulchra. J. Exp. Mar. Biol. Ecol., 23, 135-44. Arnold, D.C. 1972 . Salinity tolerances of some common prosobranchs. J. Mar. Biol. Ass. UK, 52, 475-86. Ballantine, W.J. 1961 . A Biologically Defined Exposure Scale, for the Comparative Description of Rocky Shores. Fld. Stud., I 3 , 1. Barnes, R.S.K. 1974 . Estuarine Biology. London, Edward Arnold. Barnes, R.S.K. ed. 1977 . The Coastline. Chichester, Wiley....

Diatoms class Bacillariophyceae

Dinoflagellates Amphisolenia

The majority of diatoms are unicellular, uninucleate plants with a size range of about 15 m to 400 m in maximum dimension, although some smaller and a few considerably larger forms exist. The largest known diatom is a tropical species, Ethmodiscus rex, up to 2 mm in diameter. The diatom cell, known as a frustule, has a cell wall of unusual composition and structure. It is impregnated with siliceous material giving a glassy quality and consists of two parts, the valves. At its simplest, for...

Benthos

Towed Submersible Sledge

There are several branches of science which seek information about the sea bottom for example, oceanography, geology and palaeontology as well as marine biology. Each makes use of apparatus designed primarily to collect information needed in that particular field of study, but there is so much overlap between these various aspects of marine science that data relevant to one may well be of interest to another, and there is consequently a variety of instruments for studying the sea Acoustic...

Underwater photography

Bathysnap Design

In recent years, there have been rapid advances in the development of underwater cameras, television and video. The current interest in sport diving has led to the development of a wide variety of underwater camera equipment designed for easy use by scuba divers. Further impetus has come from the need of the oil and gas industry to inspect their underwater hardware. Photography is widely used by marine biologists to support other sampling methods. It can also be used as a recording tool on its...

Herring Clupea harengus

Herring Figure 9.21 are widely distributed across the north-eastern Atlantic shelf between Newfoundland and the British Isles, and also in the Arctic. They extend south to the area of Gibraltar on European coasts, and south to Cape Hatteras on the North American coast. However, it is only in northern areas that they are sufficiently abundant to be commercially valuable. They have now become scarce in some areas, such as the North Sea where they were once immensely abundant and they now no...

The overfishing problem

Addressing the International Fishery Exhibition in London in 1883, T.H. Huxley said I believe that it may be affirmed with confidence that, in relation to our present modes of fishing, a number of the most important fisheries, such as the cod fishery, the herring fishery and the mackerel fishery, are inexhaustible. And I base this conviction on two grounds, first, that the multitude of these fishes is so inconceivably great that the number we catch is relatively insignificant and, secondly,...

Zonation patterns

Intertidal Zone Beaches Food Web

The zonation of plants and animals is often clearly visible on rocky coastlines of the British Isles. An excellent summary of 'typical' patterns of zonation on sheltered, moderately exposed and exposed shores is given in Hawkins and Jones 1992 . For a fuller picture, students should refer to Lewis 1964 where a full account is given of distribution patterns on many different shores throughout the British Isles. Other useful references include Ballantine 1961 and Moyse and Nelson-Smith 1963 ....