Spatial,temporal, and behavioral patterns in emergence of zooplankton in the lagoon of Heron Reef,Great Barrier Reef,Australia

A total of 34 zooplanktonic taxa were common in emergence trap, reentry trap, and net-tow samples taken in the lagoon of Heron Reef, Great Barrier Reef, between 27 February and 22 March and between 11 June and 4 July 1985. Twenty-nine of these taxa were classified as demersal (17 taxa), meroplanktonic and larval (10 taxa), or incidental (2 taxa). The remaining five multispecific groups yielded variable results. Differences were observed between two locations separated by 200 m, with emergence 2 to 62 times greater for 22 taxa at a deeper site with larger coral formations. Most zooplankters were more common (2 to 122 times) in samples from 1 m² areas around 0.25 to 0.5 m² patches of branching coral. However, two species of copepods, Pseudodiaptomus colefaxi and Metis holothuriae, were taken in greater numbers (3 to 12 times) from open sand. Seasonal increases (2 to 322 times) were observed for 13 adult taxa and 8 classes of larvae or juveniles in the summer and for 10 adult taxa and one larval group in the winter. Fourteen of the 17 demersal taxa and 4 groups of large larvae or juveniles emerged in numbers 2 to 323 times greater during lunar quarters or new moons. In contrast, 6 larval taxa and 4 groups of small or transparent adults displayed significant emergence during full moons. Five diurnal emergence patterns were shown by 27 taxa, with patterns varying primarily among lunar periods. The variety of taxon-specific patterns observed in this study highlight a need for caution when generalizing about demersal zooplankton.     

Influence of inter- and intra-daily light-field variability on photosynthesis by coastal phytoplankton

An investigation was carried out to determine the relationships between the principal photosynthetic parameters of natural marine phytoplankton and the properties of the irradiance of the preceding five days and the intra-daily ambient irradiance. Samples used in the study were collected from Strangford Lough, Northern Ireland during both winter and summer between 1979 and 1981. Photosynthetic parameters were determined for both constant and ambient incubation light fields. The fluctuation properties of the irradiance field exerted little influence on the photosynthetic parameters. In summer populations, the parameters obtained from morning samples were strongly influenced by the total irradiance recorded on the fourth day previous to experimentation, irrespective of the incubation irradiance. In contrast, the corresponding parameters from afternoon samples were most influenced by the total irradiance received during incubation. The influence of these two separate factors over a day may contribute to variability in the magnitude of diel changes in marine phytoplankton photosynthesis.     

The ecophysiological complex of Bathyporeia pilosa and B. pelagica (Crustacea: Amphipoda). I. Respiration rates

The metabolic rates of high and low shore estuarine populations of Bathyporeia pilosa Lindström and an open coast population of B. pelagica (Bate) have been determined over a range of temperatures during January and February, and June and July, 1968. Changes in oxygen uptake have also been measured monthly at 15°C. During the winter, oxygen uptake was in the order: high shore B. pilosa>low shore B. pilosa>B. pelagica. During the summer, high shore B. pilosa and B. pelagica had similar metabolic rates, but both were significantly higher than low shore B. pilosa. Both populations of B. pilosa had lower metabolic rates in summer than in winter, whereas the metabolic rate of B. pelagica remained much the same. Seasonal changes in metabolic rate are closely correlated with reproductive cycles. The possible influences of environmental parameters are discussed.     

Aspects écologiques de la zonation intertidale sur les côtes rocheuses des îles Galapagos

Features of the intertidal zonation on the rocky shores of the Galapagos Islands are described and discussed in relation to environmental factors, in particular temperature — which varies with regional hydrology and climatology. Owing to the thermal properties of the coastal waters and to the nature of the substrate (mainly basalt), intertidal organisms are exposed to a wide range of temperatures, which fluctuate with tide, day, and season. As a result, life is mostly restricted to the lowest levels of the shore; the middle- and upper-level populations are sparse. Local variations (biofacies) resulting from water agitation are described. Biota consist of tropical, subtropical, and warm-temperate components. Tropical species dominate in sheltered areas and in middle and upper shores.

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Contribution No. 164, the Charles Darwin Foundation.     

Effects of dietary fatty acids on the reproductive success of the calanoid copepod<Emphasis Type="Italic"> Temora longicornis</Emphasis>

Egg production and hatching success of the copepod Temora longicornis were measured in laboratory experiments and in the field (North Sea). In the laboratory, ingestion of four algal species (Thalassiosira weissflogii, Phaeocystis globosa, Isochrysis sp. and Dunaliella tertiolecta) was followed and the content of fatty acids in the algae was determined. The two food types (T. weissflogii and Isochrysis sp.) that provided the highest ingestion of carbon and long chain fatty acids also resulted in the highest egg production rate (E_r) and hatching success (H%). In contrast, D. tertiolecta led to both low ingestion of carbon and long chain fatty acids, resulting in low reproductive success. There was a positive relationship between the amount of eicosapentaenoic fatty acid [20:5(n-3), EPA] ingested and E_r and H%, and of the ratio between docosahexaenoic and eicosapentaenoic fatty acid [22:6(n-3)/20:5(n-3), DHA/EPA] in the ingested food and H%. In the field, chlorophyll a and specific fatty acids were measured and protists were enumerated, in order to investigate the link between these factors and the reproductive success of T. longicornis. Hatching time was found to be related to temperature and exceeded 120 h at 6°C. No relationship was found between chlorophyll a and reproductive success (E_r or H%). E_r correlated with the concentration of diatoms and ciliates, which were the dominating protists in early spring, indicating that food quantity was the limiting factor for E_r. As in the laboratory experiments, H% was dependent on the fatty acid DHA and the ratio of DHA/EPA, which indicates that the quality of eggs (H%) is linked to the quality of food.Communicated by M. Kühl, Helsingør     

Sex-specific energy requirements in nestlings of an extremely sexually size dimorphic bird, the European sparrowhawk (Accipiter nisus)

Allocation of parental investment is predicted to be equal at the population level between both sexes of offspring, and should lead to sex ratio biases in species that exhibit a sex-difference in parental care. Sex-differences in parental care are rarely quantified. We measured daily energy expenditure in free-living nestlings of the extremely sexually size dimorphic European sparrowhawk (Accipiter nisus), using the doubly labelled water method. These data were combined with measured growth characteristics to estimate daily and total metabolised energy intake of male and female young during the nestling stage. Females reached an asymptotic body mass 1.6 times higher than males. This resulted in a total metabolised energy an estimated 1.4 times higher for the nestling stage. Furthermore, we observed a decline in daily metabolised energy with an increase in brood size, which was significantly stronger for females than for males. These results are discussed in the context of Fishers equal allocation theory. Empirical evidence of a sex ratio bias at the end of parental care, with an overall excess of males, is lacking in this species. Consequently, our data do not support the idea of equal allocation between the sexes. The observed sex difference in daily metabolised energy in response to brood size may give scope for sex ratio bias at the level of the individual brood.     

Feeding habits of the dungeness crab Cancer magister as determined by the index of relative importance

Specimens of the Dungeness crab Cancer magister, were collected subtidally and intertidally from an estuary in Washington State, USA in June and September 1980, and January, April, May and July, 1981. Gut contens of freshly collected crabs were analyzed by the Index of Relative Importance; for each prey taxon, this method measured frequency of occurrence, percentage of total biomass, and percentage of total numbers consumed. The most important higher taxon eaten was fish; however, the most important prey genus was the shrimp Crangon spp. There was greater predation on Crangon spp. at night at the intertidal site, and during winter and spring when the shrimp were most abundant there. Feeding activity, as indicated by a weight-specific gut-fullness index, showed no consistent diel pattern. There were significant ontogenetic changes in feeding patterns: first-year crabs preyed primarily on very small bivalves or small crustaceans including their conspecifics; second-year crabs preferred Crangon spp. and fish, and third-year crabs preyed less on Crangon spp. and more on fish. Such changes in feeding habits with ege could be purely due to mechanics of food handling, but might also reduce competition among age groups of crabs, possibly partitioning resources within the estuary. Findings are discussed in terms of optimal foraging and compared to other similar studies.Contribution No. 599, School of Fisheries, University of Washington, Seattle, Washington 98195, USA     

Cadmium accumulation and toxicity in the kidney of the bay scallop Argopecten irradians

Specimes of bay scallops, Argopecten irradians, collected from shallow-water eel-grass beds near Beaufort, North Carolina (USA) in September 1979, were exposed to 0.7 ppm cadmium in flowing seawater for 5 d. This exposure resulted in a massive extrusion of the calcified concretions of most of the kidney epithelial cells, although marked morphological damage consisting of cytoplasmc degeneration was apparent in only a few focal areas of the kidney. In addition, unique cytoplasmic membrane-bound bodies were observed in epithelial cells of cadmium-treated but not control scallop kidneys. In some cells, these bodies appeared to fuse with the main concretion vacuole. Kidneys of cadmium-treated scallops accumulated cadmium to 200 ppm on a wet wt basis; of this 60% was associated with concretions (2 000 ppm dry wt) and 38% with the membranous pellet obtained after ultracentrifugation at 105 000 g for 1 h. Approximately 2% of total kidney cadmium was associated with the cytosolic fractions but, unlike zinc or manganese, which were bound to either high or low molecular weight species, a large component of the cadmium in this fraction was bound to a protein peak of approximately 21 000 daltons. Results of this study indicate that kidney concretions of A. irradians play a major role in the control of renal cadmium accumulation and excretion and hence the toxicity of cadmium to this organism.