Showing papers on "Pelagic zone published in 1987"

Ecological Studies in Tropical Fish Communities

Abstract: Preface Acknowledgements Part I: Introduction: 1. Introduction Part II. Freshwater Studies: 2. The African fish fauna 3. Man-made lakes 4. Lacustrine fish communities in the Great lakes of eastern Africa 5. Speciation: the African Great lakes as laboratories of evolution 6. The Neotropical fish fauna 7. Far Eastern freshwater fish faunas and their distributions Part III. Marine Fish Studies: 8. Underwater observations: coral reef fishes 9. Demersal fish studies 10. Pelagic fishes Part IV. Syntheses: 11. Responses of fishes to conditions in tropical waters 12. Trophic interrelationships 13. Diversity: its maintenance and evolution 14. The exploitation and conservation of tropical fish stocks Appendix References Index.

New Perspectives on the Pelagic Stage of Sea Turtle Development

Abstract: An original difficulty in accepting the idea of a pe- lagic developmental period for sea turtles was to explain how food could be found in reliable supply in the open ocean The uncertainty that this introduced was removed when I belatedly came to appreciate theprevalence and diversity of convergences where downwelling gathers and aligns buoyant material, in- cluding the dispersedfood resources of the surface waters. Thus, it now seems clear that an essential factor in the survival of young sea turtles-and of other elements of the epipelagic, open-oceanfauna as well-is the accessibility of afront, where inanimate debris and any floating animal or plant will be gathered in This new evidence of complexity in the lost-year ecology of sea turtles has important implications for their conservation and management. It is now obvious that when young cultured sea turtles are released in so-called head-starting projects, the release sites ought to be chosen with the greatest care. Shores located at a distance from any major current or its eddy ought to be avoided It is also necessary to avoid release localities where the convergence habitat may carry heavy loads of pol- lutant& Results of the present work reveal an urgent need for further study of sea turtle life cycles, with special attention to their developmental ecology. The growing evidence for a more pro- tracted pelagic stage, during which the juvenile turtles are pas- sive migrants in fronts that are increasingly invaded by debris

The causes of buoyancy in eggs of marine teleosts

Abstract: Pelagic eggs and demersal eggs of teleosts both have osmotic concentrations similar to that of the maternal body fluids, less than half that of sea water. Pelagic eggs are buoyant because they contain such large quantities of this dilute aqueous fluid. While the demersal eggs of teleosts usually have a water content of 60–70%, the buoyant pelagic eggs of marine teleosts such as whiting, Norway pout, saithe, cod, haddock, turbot, dab, plaice, witch, long rough dab, halibut and sole typically have a very high water content (ca. 92 %) and a lipid content of 10–17% of egg dry weight. About 90% of the buoyancy of such eggs in sea water is caused by their high aqueous content, only about 10% being caused by lipid. The buoyant eggs of grenadier and ling have large oil globules and higher lipid contents, 27 and 35 % of dry weight respectively. Nevertheless, most of their buoyancy is provided by their high aqueous contents (89 and 81 % water). The high water content of pelagic eggs is brought about by a massive influx of water into the oocytes during meiotic maturation (ripening) after vitellogenesis but before ovulation. In cod and plaice, ripening is accompanied by a four- to five-fold increase in both water content and free amino-acids, and by a large influx of both potassium and sodium. In cod, free amino-acids contribute much more than these inorganic ions to the water influx and to the total osmotic concentration of the mature egg, but in plaice the relative contribution of inorganic ions approaches that of the free amino-acids.

Resuspension in the shallow sublittoral zone of a macrotidal estuarine environment: Wind influence1

Abstract: Several biological and physical variables were measured four times daily for 148 consecutive days at a fixed station to examine fluctuations of phytoplankton abundance in the littoral zone of the lower St. Lawrence estuary. On the seasonal scale, the pattern of variation of phytoplankton was characterized by a midsummer diatom bloom similar to that observed offshore in the pelagic zone. On the shorter time scale, chlorophyll a concentration in the littoral zone was highly variable and closely associated with variations in the wind field. No relationship, however, could be found between phytoplankton cell numbers and wind velocity. The possible influence of wind, tidalinduced upwelling, overturning eddies, and wave-induced mixing processes on resuspension was examined. The higher Chl a values observed irregularly at the sampling stations resulted from the mechanical resuspension of benthic diatoms due to wind, or wind-induced wave, mixing in the littoral zone. Wind velocities >4 m s-l were shown to cause significant resuspension of particulate organic matter (POC) in the water column. For winds >6 m s-l, there was no further increase in POC. These results suggest that the frequency of wind velocities > 4 m s- * plays a significant role on secondary production in the littoral zone by providing an increased food supply to benthic and planktonic filter feeders, especially at times when phytoplankton biomass is normally low in the water column.

Diets of fishes of the upper continental slope of eastern Tasmania: content, calorific values, dietary overlap and trophic relationships

Abstract: Diets of 15 species of demersal and pelagic fishes on the upper continental slope (420 to 550 m) were determined, based on samples taken every two months over 13 mo (April 1984 to April 1985) off eastern Tasmania. The calorific contribution of each prey item to the diets was determined. The fish could be divided into four trophic categories: pelagic piscivores, epibenthic piscivores, epibenthic invertebrate feeders and benthopelagic omnivores. Dietary overlap between the groups was low. The pelagic piscivores Apogonops anomalus, Trachurus declivis, Brama brama, Lepidopus caudatus and Macruronus novaezelandiae primarily consume the shelf-break myctophid Lampanyctodes hectoris; their diet is narrow, with a large overlap between species. The epibenthic piscivores Deania calcea and Genypterus blacodes both take a greater variety of prey, but have little dietary overlap. The fish feeding on epibenthic invertebrates, Coelorinchus sp. 2 and Centriscops humerosus, obtain most of their energy from benthic Crustacea and Ophiuroidea, supplemented with Lampanyctodes hectoris; the diet is broad, with little overlap. Among the benthopelagic omnivores (Cyttus traversi, Coelorinchus sp. 4, Lepidorhynchus denticulatus, Neocyttus rhomboidalis, Helicolenus percoides, Epigonus denticulatus and E. lenimen), most diets are broad and show slight overlap. All but E. denticulatus consume significant quantities of Lampanyctodes hectoris as well as Crustacea, particularly Polychaeta, Euphausiacea and Pyrosoma atlanticum. Seasonal changes in diet occurred in G. blacodes, T. declivis, Lepidopus caudatus, Coelorinchus sp. 4, Lepidorhynchus denticulatus, H. percoides, E. denticulatus and E. lenimen; these were related to changes in abundance of particular prey species, not to alterations in feeding habits. Only three species, Lepidopus caudatus, Coelorinchus sp. 2 and H. percoides, showed significant diel feeding periodicity. Ontogenetic dietary changes were evident in Cyttus traversi, Coelorinchus sp. 2, Lepidorhynchus denticulatus and H. percoides. Cyttus traversi and H. percoides progressively changed from crustaceans to fish as their size increased. The diets of size classes within species showed little overlap, except for Lepidorhynchus denticulatus, which eats chiefly euphausiids and Lampanyctodes hectoris at all sizes. In addition to describing the diets and trophic relationships of 90% of the fish biomass, the results emphasize the importance to the entire fish community of mesopelagic food resources, particularly Lampanyctodes hectoris. Many benthopelagic species undertake extensive vertical migrations in search of prey, thus playing a major role in the transport of energy from midwater regions to the benthos of the continental slope.

Seasonal variation in the diet of the king penguin (Aptenodytes patagonicus) at sub-Antarctic Marion Island

Abstract: The diet of the king penguin Aptenodytes patagonicus at Marion Island was examined throughout the year by analysis of stomach samples. Fish accounted for 87% by wet mass, 75% by numbers and 69% by reconstituted mass. Their proportional importance by wet mass increased from 68% during winter to almost 100% in summer and probably reflects a real increase in their local availability. Squid comprised most of the remainder with crustaceans forming less than 1% of the diet by numbers. Prey items were generally small, the most abundant being three species of myctophid fish, Krefftichthys anderssoni, Protomyctophum tenisoni and Electrona carlsbergi, and a squid Kondakovia longimana. King penguins took both juvenile and adult Krefftichthys anderssoni and P. tenisoni, but only adult E. carlshergi. The juvenile and adult modal size classes of K. anderssoni and P. tenisoni increased from March through to February and the proportion of juvenile to adult fish increased in winter. The increase in the modal size class of the K. anderssoni/P. tenisoni complex during the year probably reflects growth of the fish, rather than movement of different populations in and out of the area exploited by king penguins. All squid consumed were probably juveniles. The modal size class of Kondakovia longimana increased from March to August, but in September to October smaller squid again formed a large proportion of the squid component of the diet. Numbers of measurable squid beaks recovered from November to February were low. This is the first time that mesopelagic myctophid fish have been shown to comprise a major component of the diet of a vertebrate predator in the Southern Ocean. Summary King penguins are important consumers of marine resources, throughout the year, at the Prince Edward Islands. Meal size varied from 8.5–12.6% of adult mass, depending on the method of determination. In spite of the biases in the analysis favouring the overestimation of squid, fish and, in particular, myctophid fish accounted for the largest proportion of the stomach samples, 87% by wet mass, 75% by numbers and 69% by reconstituted mass. The relative abundance of fish in the diet dropped markedly in winter followed by a subsequent rise to nearly 100% in summer. This rise coincided with an increase in the chick growth rate and the king penguin population at the island and suggests the rise in relative abundance offish reflects a real increase in the availability of fish around the islands. Juvenile and adult Krefftichthys anderssoni/Protomyctophum tenisoni and adult Electrona carlsbergi were the most common fish consumed. There was an increase in the modal size of K. anderssoni/P. tenisoni throughout the year which we interpret as growth of a single fish population. Juvenile Kondakoviu longimana was the important squid species taken by king penguins. Crustaceans were only rarely recorded in the diet and may have come from digestion of fish and squid stomachs. This is the first study of the diet of a Southern Ocean pelagic predator that has identified myctophid fish as a major component of its diet. All three important fish species taken by king penguins at Marion Island have a wide distribution throughout the Southern Ocean and consequently may prove to be important dietary components of other Southern Ocean pelagic predators.

Trophic relationships in the demersal fish community off Namibia

Abstract: The benthic fish community off Namibia (between the Cunene River and Walvis Bay) in 50–650 m of water was studied during three bottom trawl surveys. The community was investigated on the basis of distribution, abundance and diet of 51 species, constituting 95 per cent of the demersal fish biomass. Dietary studies revealed the existence of three major trophic groups, one containing species that prey on pelagic and nektonic organisms, a second dominated by predators that feed on benthic polychaetes and copepods and a third group containing predators of benthic crabs, demersal shrimps and fish. Well differentiated from these groups are a few species that prey mainly on jellyfish and ophiuroids. Because for most of the species, their trophic level changes with growth, they were divided into size classes which are analysed independently. To describe interactions between the size classes, a similarity index combining diet affinity with spatial coincidence was applied. Cluster analysis showed that, for Merlucciu...

Habitat use of arctic charrSalvelinus alpinus in Thingvallavatn, Iceland

Abstract: Habitat use by four morphs of arctic charr,Salvelinus alpinus, was investigated in Thingvallavatn, Iceland, by sampling with pelagic and benthic gill nets. Sampling was done in May/June and August/September. Greatest abundance of fish was recorded in the littoral and epipelagic zone in early autumn. Catches were low in early summer. The four morphs are partly segregated in habitat. Small (SB-) and large benthivorous (LB-) charr have a more restricted spatial distribution than piscivorous (PI-), and especially planktivorous (PL-) charr. Both benthivorous morphs are mainly found in the littoral zone, and occur in largest numbers in stony shallows at depths between 0 and 10 m. PL-charr usually dominates in numbers in all habitats. PI-charr is most abundant in epibenthic habitats, although numbers are always low. All morphs are caught in higher numbers at night than during the day, but the diurnal activity difference is highest among SB-charr. The habitat use by different morphs is as may be expected from their morphology and diets. Within the population of PL-charr, young and small fish are more abundant on the bottom than in the pelagic zone, and there is a surplus of females in the pelagic zone. Along the benthic profile, young, small and immature PL-charr are more abundant in deep than in shallow waters. The results are discussed in relation to food supply, competition and predation. Possible reasons for the occurrence of four arctic charr morphs are also discussed.

Continuous plankton records: the geographical distribution and seasonal cycles of decapod crustacean larvae and pelagic post-larvae in the north-eastern Atlantic Ocean and the North Sea, 1981–3

Abstract: The geographical distributions and seasonal cycles of pelagic larvae and post-larval stages of decapod Crustacea in the north-eastern Atlantic and the North Sea during 1981–3 are described from samples taken with the Continuous Plankton Recorder (CPR). Analyses of the distributions of 36 common taxa identified groupings which could be related to depth and temperature. The seasonal occurrences of planktonic larvae of benthic taxa were found to be correlated with sea-bottom temperature in the winter as well as parameters of the sea-surface temperature. Possible interpretations of these data are discussed.

Late austral spring diatom distribution between New Zealand and the Ross Ice Shelf, Antarctica; hydrographic and sediment correlations

Abstract: Six diatom assemblages were identified in 10 surface water samples taken along a north-south track in December 1976, between New Zealand and the Ross Ice Shelf. These were further divided into two groups, whose boundary is approximately marked by: 1) the 0?C sea surface isotherm; 2) a surface salinity minimum; 3) the northward limit of high-silicate surface water; and 4) the presence of sea-ice to the south. The northern group (two assemblages) is characterized by open ocean forms while the southern group (four assemblages) is characterized by ice-edge and near-ice forms. Diatom abundance along this track appears to be dictated by temperature and nutrients and the damping effects of sea-ice on surface water productivity. We could not, however, rule out other factors such as differing nutrient concentrations and proportions and water column stability. A number of surface water assemblages could also be observed in the underlying surface sediments after allowing for dissolution in the water column and the homogenizing effects of deep and bottom water currents.

The influence of predation on horizontal distribution of zooplankton species

Abstract: SUMMARY. 1. The horizontal distributions of Daphnia longispina and Bosmina tongispina in Lake Kvernavatn (Norway) were investigated twice in 1982. In late spring, when populations were small, the two species inhabited the same areas, and they were evenly distributed from the littoral to the pelagic. At high population densities, during midsummer, the species were spatially segregated, D. longispina being pelagic and B. longispina littoral in distribution. 2. The distribution and feeding of three-spined sticklebacks (Gasteros-teus aculeatus) were also studied. The sticklebacks were apparently forced into littoral areas by larger piscivorous predators in the pelagic and they were consequently restricted to foraging primarily on B. longispina, which formed dense swarms during daytime in summer. 3. We suggest that predation and competition influence the spatial distribution of zooplankton species. The feeding efficiency of fish foraging on high-density zooplankton populations can be reduced by spatial segregation of zooplankton species. Where high local densities occur, due to swarm formation, predation is changed from size-selective feeding to consumption of spatially isolated individuals.

Patterns of larval drift in southern california marine shore fishes inferred from alwzyme data

Abstract: ABSTRACf A multispecies analysis of allozyme data for 10 marine shore fishes was undertaken to identify patterns of genetic differentiation resulting from.larval drift. Previous studies suggest that allele frequencies in these fishes are sensitive primarily to the effects of migration, rather than to natural selection or historical factors. The following patterns recur in most species: 1) Two northern populations (La Jolla, California, and the California Channel Islands) share a relatively high genetic affinity with all other populations, while the two southern populations (Isla de Guadalupe and Punta Eugenia, Baja California, Mexico) are relatively divergent; 2) the two southern populations apparently exchange genes much more frequently with northern populations than with each other; 3) anomalous results for the ocean whitefish, Caulolatilus pri'ICep8, can be understood on the basis of known patterns of larval distribution in this species. The consistency of these large-scale patterns among species with markedly different life history features and dispersal capabilities suggests that the results obtained here may provide insight into the population structure of other species (invertebrates as well as fish) with pelagic larvae. Two characteristics of shallow-water marine organ­ isms make the analysis of their population structure interesting and challenging. First, adults of these species are restricted to relatively shallow, inshore waters, so adult populations can be isolated from other populations by expanses of deep water or areas of otherwise unsuitable habitat. On the other hand, many marine species have a pelagic larval stage lasting several weeks or months and thus at least the potential for long-distance transport by ocean currents. Indeed, such long-distance disper­ sal events are generally invoked to explain the pres­ ence of shallow-water marine organisms on oceanic islands isolated by up to several thousand kilometers from possible sources of propagules. However, very little is actually known concern­ ing the complex process of larval drift, and several questions remain largely unanswered. For example, by what pathways do larvae traverse oceanic barriers separating different populations? Further­ more, do recruits arrive at remote areas on a more­ or-less continuous basis, or is long-distance disper­ sal the result of rare or unique "sweepstakes" events? The answers to these questions are relevant not only to evolutionary biologists seeking to under­ stand the processes of differentiation and specia

Seasonal occurrence of larval fishes in the nearshore Southern California Bight off San Onofre, California

Abstract: Larval fishes were sampled from the nearshore region of the Southern California Bight off San Onofre for 29 months and analyzed with a Curtis-Bray Cluster Analysis to determine temporal assemblages and species associations. Two major assemblages of larvae were found: members of the winter-spring (December-May) assemblage were most abundant from January to May; members of the summer-fall (June-November) assemblage were most abundant from July to September. The winter-spring assemblage was composed primarily of Engraulis mordax, Genyonemus lineatus, Sebastes spp. and Paralichthys californicus ; some abundant taxa in the summer-fall assemblage were Seriphus politus, Paralabrax spp., and Hypsoblennius spp., although E. mordax again predominated. Demersal spawners tended to have spawning seasons of longer duration than pelagic spawners; winter-spring spawners generally had longer spawning seasons than summer-fall spawners. We suggest that temperature is an important determinant in the seasonal pattern of larval fish occurrence. The annual ocean temperature cycle near San Onofre was a good indicator of the seasonal occurrence of fish larvae in this area. Larvae found in the cooler months were generally offspring of adults whose northern ranges extend to Canada. Warm-water larvae were offspring of adults whose northern ranges extend to Point Conception or northern California.

Growth rates in culture of several species of Sargassum from Florida, USA

Abstract: When suitable substrate is present, benthic species of the brown algal genus Sargassum are often pre-dominant components of shallow subtidal communities in tropical and subtropical waters (Tsuda, 1972; Wanders, 1976; Connor & Adey, 1977; Cordero, 1981; Morrissey, 1980). Such is the case in shallow subtidal areas of Florida and Caribbean waters where at least twelve benthic species of Sargassum occur (Taylor, 1960). In addition, two pelagic species, S. fluitans Borgesen and S. natans (Linnaeus) Gaillon, can form large accumulations in the Sargasso Sea, the Gulf Stream, and the Gulf of Mexico, although the average standing crop of these species over these vast areas is quite low (Parr, 1939). Most previous investigators (e.g., Howard & Menzies, 1969; Carpenter & Cox, 1974; Blake & Johnson, 1976; Mann et al., 1980) believe that the productivity of pelagic Sargassum is quite low, but recent research (Lapointe, 1986) has demonstrated that the growth rate and productivity of these species can be much higher than previously reported, with rates approximating those of productive benthic macroalgae.

Mesopelagic fish derivatives in the southern Benguela upwelling region

Abstract: Discussion of mesopelagic fish within the southern Benguela system necessitates recognition of both oceanic and neritic realms, demarcated by the continental shelf-break. In the eastern South Atlantic (FAO Area 47), the stock size of two oceanic, mesopelagic families (Myctophidae, Sternoptychidae) have been estimated at 8–12 million and 750 000 metric tons respectively. Each possesses pseudoceanic species, populations of which constitute a possible alternative fishery resource to conventional pelagic stocks. Of these upper-slope/shelf derivatives, Lampanytodes hectoris (Myctophidae) and Maurolicus muelleri (Sternoptychidae) are most abundant. In the southern Benguela system (Orange River mouth to Cape Point), both species appear to be restricted mainly to the region east of the offshore divergence, corresponding roughly to the continental shelf-break. Maurolicus muelleri has not been taken by the fishery, but purse-seine landings of Lampanyctodes hectoris have accounted for up to some 10 per cent of the t...

Big Soda Lake (Nevada). 2. Pelagic sulfate reduction

Abstract: The epilimnion of hypersalinc, alkaline, meromictic Big Soda Lake contains an average 58 mmol sulfate liter-’ and 0.4 pmol dissolved iron litcr- I. The monimolimnion, which is permanently anoxic, has a sulfide concentration ranging seasonally from 4 to 7 mmol liter-l. Depth profiles of sulfate reduction in the monimolimnion, assayed with a 35S tracer technique and in situ incubations, demonstrated that sulfate reduction occurs within the water column of this extreme environment. The average rate of reduction in the monimolimnion was 3 Fmol sulfate liter-r d-’ in May compared to 0.9 in October. These values are comparable to rates of sulfate reduction reported for anoxic waters of more moderate environments. Sulfate reduction also occurred in the anoxic zone of the mixolimnion, though at significantly lower rates (0.025-0.090 pmol liter-l d-l at 25 m). Additions of FeS (I .O mmol liter I) doubled the endogenous rate of sulfate reduction in the monimolimnion, while MnS and kaolinite had no effect. These results suggest that sulfate reduction in Big Soda Lake is iron limited and controlled by seasonal variables other than temperature. Estimates of the organic carbon mineralized by sulfate reduction exceed measured fluxes of particulate organic carbon sinking from the mixolimnion. Thus, additional sources of electron donors (other than those derived from the sinking of pelagic autotrophs) may also fuel monimolimnetic sulfate reduction in the lake.

Marine food and diet overlap of co-occurring Arctic charr Salvelinus alpinus (L.), brown trout Salmo trutta L. and Atlantic salmon S. salar L. off Senja, N. Norway

Abstract: Stomach contents analyses and other biological information of Arctic charr (Savelinus alpinus (L.)), brown trout (Salmo trutta L.) and small Atlantic salmon (S. salar L.) caught 1982–85 close to the Aelv estuary (69°N) on the island of Senja, N. Norway are presented, and extracts of a 1975–85 fishing log given. this appears to be the first case study of the feeding habits of all three European anadromous salmonids in marine sympatry, and also one of very few reports on the marine food of the Arctic charr from Europe. The general feeding habits of the charr were similar to that found in N. Canada. Pelagic fish (herring, sand-eel) seem to be preferred. Plankton (crab megalopae, krill) and hyperbenthos (amphipods, mysids) are also taken, especially when suitable fish are scarce. In 1985 high herring densities provided superabundant food, and diet overlap between charr, trout and salmon was high. Salmonid nursery rivers are abundant in N. Norway and during summer the three species coexist in a near-shore, surface-oriented pelagic guild of fishes. The salmon seems to be a relatively specialized piscivore, while the trout takes a wider range of fish and also invertebrate prey. The charr probably is the most euryphagous of the three, being able to exploit the more marginal parts of the prey resources of their common habitat.

The size distribution of organisms in the Celtic Sea: from bacteria to Metazoa.

Abstract: The main features of the size distribution of pelagic and benthic organisms are described, with particular reference to comprehensive studies at a single station, CS2, in the Celtic Sea. These are: 1. A more or less even distribution of biomass in all size classes of pelagic autotrophs. 2. Five size groups of pelagic heterotrophs separated from each other by roughly 103 differences in individual weight, with three well-defined gaps in the size spectrum between the four smallest size modes. 3. Benthic organisms with three size modes, the microbial peak between the two smallest pelagic modes, the meiofaunal peak between the size of pelagic ciliates and herbivorous macrozooplankton, and the macrobenthic peak at about the same size as the carnivorous macrozooplankton. Differences in the positions of the microbial peaks are thought to be associated with the different nutritional environments of free-living and surface-attached bacteria. Other features of the pelagic heterotroph spectrum are explicable in terms of the known limits to size ratios between prey and predator for suspension feeders. These limits do not apply to the benthos, the size distribution of which is largely determined by physical constraints of the sedimentary environment and the optimisation of size-related life history characteristics. Thus, constraints on body size are entirely different in the two systems, and we see little evidence for coupling between the pelagos and benthos which might result in complementary patterns of size distribution, except perhaps for interactions between the pelagic larvae of macrobenthos and the permanent macrozooplankton at the upper end of the size spectrum.

Implications of fecal pellet size and zooplankton behaviour to estimates of pelagic-benthic carbon flux

Abstract: Numbers, volumes and carbon content of fecal pellets collected by sediment traps and bottle casts were measured with an image analysis system, from samples collected in the lower Bay of Fundy, Atlantic Canada. Analysis of sinking, resuspension and biodegradation rates indicated that small fecal pellets must be heavily grazed within the water column. Measurement of rates of coprophagy and vertical distribution of pellets without peritrophic membranes may lead to estimates of resuspension. Differences in size-frequency spectra of pellets collected in 5 h and 24 h sediment trap developments indicated that large fecal pellets which reach the benthos are produced primarily by migratory copepods and euphausids. The effects of diel vertical migration may bias estimates of pellet carbon flux made from short sediment-trap deployments.

Oceanography: An Introduction to the Marine Environment

Abstract: List of boxes. Part 1 Introduction to the world ocean: major features of the Earth plate tectonics. Part 2 Basic principles of oceanography: physical and chemical properties of sea water circulation systems of the world waves tides the marine biological environment life in the sea marine geology and geophysics. Part 3 Coastal environments: estuaries and related environments deltas barrier island complexes rocky coasts. Part 4 Open marine environment: reefs continental shelf outer continental margin the pelagic environment the floor of the ocean basins. Part 5 Applied oceanography: resources of the sea human impact on the marine environment. Appendixes: conversions and constants general classification of marine organisms.

The migration of ultrasonic‐tagged bream, Abramis brama (L), in Lake Constance (Bodensee‐Untersee)

Abstract: From May to October 1983 the migration of six adult bream was examined by long-term ultrasonic tagging experiments. Two different migration types were observed: diurnal rhythmical migrations between the littoral and pelagic zones, and sporadic locomotions such as spontaneous excursions of several kilometers distance. At night, during their sojourn in the shallow littoral zone, bream feed intensively on benthic organisms; during their stay in the pelagic areas they presumably feed on zooplankton. Sporadic changes of place enable the bream to feed on locally abundant food resources. During the spawning season, migration contributes to successful spawning.

Microbial regeneration of ammonium in the water column of Davies Reef, Australia

Abstract: Ammonium regeneration by rnicroheterotrophs was measured during winter in the water column of Davies Reef, on the Great Barrier Reef. Regeneration rates were among the lowest reported. ranging from undetectable to 0.0112 pm01 NH:-N 1-' h-'. Regeneration was highest inside a patch reef (0.0112), followed by reef flat (0.0050), lagoon (0.0017) and fore-reef (0.0013 pm01 NH:-N I-' h-' ). Bacteria and heterotrophic nanoplankton accounted for 40 to 88 % of the NH: regenerated in 208 pm filtered water. There was a trend of increasing importance of these organisms as water passed from the fore-reef, across the reef flat, and into the lagoon and patch reef areas. Remineralization was highest where water was in most intimate contact with the reef benthos, which may reflect a response of the pelagic community to the input of organic matter (e.g. mucus) to the water column by the reef benthos. A first approximation of the relative importance of bacteria versus heterotrophic nanoplankton in NHZ regeneration, established from measures of biomass and growth rates for both groups, suggested that suspended bacteria were about an order of magnitude more important than nanoplankton. Pelagic ammonium regeneration supplied almost 3 times more inorganic N to the water column in lagoonal portions of the reef than sediment nutrient regeneration did. Only over the reef flat was pelagic NH; regeneration sufficient to fully meet calculated phytoplankton N demands. Long biologically-mediated turnover times of NH: (21 to 154 h) suggest a greater importance of physical rather than biological processes in the water column of this reef during winter.

Seawater sediment interactions in coastal waters: an interdisciplinary approach

Abstract: 1: Bathymetry and Sediments of Kieler Bucht.- 2: The Pelagic System.- 3: Aspects of Benthic Community Structure and Metabolism.- 4: Diagenesis and Exchange Processes at the Benthic Boundary.- 5: Sedimentary Records of Benthic Processes.- 6: Biogenic Carbonates in Temperate and Subtropical Environments: Production and Accumulation, Saturation State and Stable Isotope Composition.- Literature.