Simulated sequestration of industrial carbon dioxide at a deep-sea site: Effects on species of harpacticoid copepods

One proposal for alleviating global warming is to sequester large amounts of industrial carbon dioxide on the deep-sea floor, but the environmental consequences of sequestration for the animals living in the sediment are poorly known. In an earlier publication, we reported that, during an experimental sequestration off central California (36.378°N, 122.676°W, 3262 m depth), most individuals of our target taxon (the harpacticoid copepods) were killed, but ∼ 20% survived. Because knowledge of which species survived and how they did so could clarify the effects of sequestration on the fauna, we have now identified the individuals from that experiment to species. Although most were adversely affected, species differed significantly in the degree of their susceptibility. Unexpectedly, six species showed no effect and may be resistant. The hypothesis that harpacticoids could escape the effects of carbon dioxide-rich seawater by moving deeper into the seabed was not supported. Exposure to carbon dioxide-rich seawater created partially defaunated areas, but we found no evidence that disturbance-exploiting harpacticoid species invaded during the recovery of the affected area. Because the environmental effects of the carbon dioxide (e.g. unusually acidic pore water) were still present, however, the opportunity for invasion might not yet have occurred. Differences among species in susceptibility increase the complexity of the effects of carbon dioxide sequestration on the deep-sea fauna.     

The influence of visibility and escape ability on sex-specific susceptibility to fish predation in Eudiaptomus gracilis (Copepoda,Crustacea)

The susceptibility to fish predation in males, ovigerous, and non-ovigerous females of the freshwater copepod Eudiaptomus gracilis is investigated in the laboratory by direct observation of the predation sequence of zebrafish, and by studying mortality when confronted with zebrafish or roach. Ovigerous females had the highest encounter rate indicating that the highly visible egg-clutch is a major determinant of their susceptibility. Males were least successful in escaping, the main reason being their inability or disinclination to react fast enough when attacked. This difference in escape reaction may have evolved because of sex-specific requirements in mate encounter and mate location. Ovigerous females and males had higher mortality than non-ovigerous females in all experiments while ovigerous mortality was higher than male mortality only in the zebrafish experiments. Neither experiment showed any difference in male and overall female mortality but as a consequence of the abrupt change in susceptibility between the ovigerous and non-ovigerous condition, it follows that sex-specific mortality rates may be dependent on the reproductive condition within diaptomid populations. A consequence of the sex-specific difference in escape ability is that the sex-specific mortality may be influenced by variation in the attack efficiency within and among predator populations.     

Microcrustacean communities in streams from two physiographically contrasting regions of Britain

ABSTRACT. Benthic microcrustaceans were sampled from forty-three streams in two physiographically contrasting regions of Britain: lowland southern England and upland Wales. Lowland streams had a significantly higher species richness than upland streams and, of the forty-three copepod and cladoceran species identified, only fourteen (33%) were found in both the lowlands and uplands. Canonical correspondence analysis revealed large differences in community structure between regions and between streams within regions. Differences within regions were related to pH, the distance downstream of a site and the presence of upstream impoundments. Variables underlying the large biological differences between regions are also discussed, including differences in chemistry (ionic content), physical parameters (e.g. flow), habitat availability and the influence of species biogeography. The importance of understanding species ecology and biogeography when assessing pollution impacts on stream communities is emphasized and a model is proposed for predicting the composition of microcrustacean communities in temperate European streams.     

Effect of inbreeding and salinity on quantitative characters and asymmetry of Tisbe holothuriae (Humes)

Effects of differing salinities on morphological characters have been found in marine and brackish populations of Tisbe holothuriae. The results suggested an active role of salinity as a factor promoting divergence. In order to test if the observed differentiation could be due to the level of heterozygosity, a study was performed in strains with low and high homozygosity. Six quantitative traits, and their respective fluctuating asymmetry, have been measured in outbred (coefficient of consanguineity, F = 0) and inbred (F = 0.5) strains, raised at three salinities; 20, 25 and 35. The analysis of variance was applied to test if the morphological measures were the same, and if the variations induced by decreased salinity had the same trend, in the two strains. Wilcoxon test was applied to the asymmetry, when it was not possible to render the variances homogeneous. The results showed that the measures and the effects of salinity on morphometry differed in the strains with low and high homozygosity. No effect of salinity on asymmetry was found. Length measures showed higher asymmetry in the most homozygous strain.     

Harpacticoid copepods associated with the seagrass Halophila ovalis in the Ashtamudi Estuary,south-west coast of India

A temporal study of harpacticoid copepod populations associated with the seagrass Halophila ovalis was undertaken in the Ashtamudi Estuary, south-west coast of India. A total of 19 species representing 8 families was recorded in this assemblage. Harpacticoids formed 7.52% of the total phytal meiofauna. At the species level, harpacticoids exhibit parallel assemblages with phytal zones, found in other localities.     

Summer-winter differences in copepod distribution around South Georgia

Zooplankton was sampled on a synoptic grid of stations centered on South Georgia during the austral summer of 1981/82 and winter 1983. Within the top 1000 m layer at oceanic stations, copepods averaged 48% of the total biomass in summer and winter, but outnumbered all other taxa combined by a factor of 10. In winter the mean zooplankton biomass within the top 1000 m was 68% of its summer level. Copepod biomass was 77% of its summer level. During both surveys, the large and abundant Calanoides acutus and Rhincalanus gigas dominated the copepod biomass and, with several other species, showed a marked downwards seasonal migration out of the top 250 m layer in winter. Antarctic epipelagic species predominated around the island during summer but tended to be replaced by sub-Antarctic and cosmopolitan species during the winter. Factors likely to influence our estimates of overall copepods abundance and changes in species composition include seasonality of reproduction, net mesh selection and differences in water mass distribution. The observed trends are attributed mainly to variation in the position of the Polar Front which lay north of the island during the summer survey yet lay across the survey area in winter. This resulted in a greater influence of sub-Antarctic water around South Georgia in winter and the displacement of Antarctic species.     

Effect of lipid reserves on individual carbon content of two planktonic freshwater copepod species

The effect of the variation of lipid droplet volume on individual carbon content was studied in two species of planktonic freshwater copepods, Eudiaptomus gracilis G.O. Sars and Thermocyclops oithonoides G.O. Sars. It was found, that when a multiple regression of carbon content on prosoma and lipid droplet volume instead of a simple regression of carbon content on prosoma volume was applied, the unexplainied variance of individual carbon content of Eudiaptomus gracilis could be reduced. However, the use of multiple regression on Thermocyclops oithonoides data did not lead to significantly higher coefficient of determination than was obtained by using a simple regression.     

Badijella jalzici - a new genus and species of calanoid copepod (Calanoida, Ridgewayiidae) from an anchialine cave on the Croatian Adriatic coast

A new genus and species of calanoid copepod belonging to the family of Ridgewayiidae is described from an anchialine cave on the small island of Badija, Croatia. In the new species Badijella jalzici, body length varies from 720-870 µm in both sexes. The prosome is 6-segmented, the female urosome is 4-segmented and 5-segmented in the male. The antennules are symmetrical and 26-segmented in the female, and 23-segmented on right side in the male, with two areas of geniculation. The caudal rami are symmetrical and longer than wide. The mouthparts and swimming legs 1-4 are identical in both sexes. The female fifth leg is biramous and symmetrical; the male fifth legs are strongly developed, asymmetrical, biramous on both sides, endopods 2-segmented and exopods 2-segmented and complex in structure.     

A matter of timing: heat wave impact on crustacean zooplankton

1. Climate change has affected zooplankton phenology and abundance in many freshwater ecosystems. The strong temperature anomalies that characterise summer heat waves make these events particularly suitable to study the effects of different seasonal warming patterns on zooplankton. Since heat waves are expected to occur more frequently under continuing climate change, they may also allow us to investigate how freshwater systems will be affected in the future. 2. Using a long‐term data set (1991–2007) from a shallow, eutrophic lake in Germany, we identify time periods in spring and summer during which cyclopoid copepods and bosminids are particularly sensitive to changes in water temperature. Based on this knowledge, we consider why summer populations responded differently to recent heat wave events that occurred at different times in the season. 3. Linear regressions of moving averages suggested that water temperatures shortly before and shortly after the clear‐water phase (CWP) were crucial for summer development of bosminids and cyclopoid copepods, respectively. Algal food availability (diatoms and cryptophytes) in the first weeks after the CWP also strongly influenced the summer populations of the two zooplankton groups. 4. Inter‐annual differences in water temperature during the critical time periods at least partly explained the contrasting responses of cyclopoid copepods and bosminids to heat wave events. 5. Our findings indicate that the zooplankton response to climate warming, particularly to heat wave events, is critically dependent on the temporal pattern of elevated water temperatures. Beyond that, we show that the summer zooplankton populations react to periods of warming in relation to events in the plankton annual cycle (such as the CWP in eutrophic lakes) rather than to warming at a fixed time in the season.     

Seasonal adaptations and the role of lipids in oceanic zooplankton

Oceanic zooplankton species exhibit quite diverse life history traits. A major driving force determining their life strategies is the seasonal variability in food supply, which is most pronounced in polar oceans where fluctuations in primary production are extreme. Seasonal adaptations are closely related to the trophic level of zooplankters, with strongest pressures occurring on herbivorous organisms. The dominant grazers, calanoid copepods and krill (Euphausiacea), have developed fascinating solutions for successful overwintering at higher latitudes. They usually exhibit a very efficient storage and utilization of energy reserves to reduce the effect of a highly seasonal primary production. The predominant larger Calanus species from the Arctic and Calanoides acutus from the Antarctic biosynthesize large amounts of high-energy wax esters with long-chain monounsaturated fatty acids and alcohols (20:1 and 22:1 isomers) as major components. They survive the dark season at depth in a stage of dormancy called diapause. In contrast, the Antarctic Calanus propinquus, a winter-active species, synthesizes primarily triacylglycerols, which are dominated by long-chain monounsaturated fatty acids with 22 carbon atoms (2 isomers) and yield even higher calorific contents. The omnivorous and carnivorous species, which are less subjected to seasonal food shortage, usually do not exhibit such an elaborate lipid biosynthesis. Herbivores usually do not utilize much of their enormous lipid reserves for overwintering, but channel this energy towards reproductive processes in late winter/early spring. Timing of reproduction is critical especially at high latitudes due to the short production period, and lipid reserves ensure early spawning independent of external resources. These energetic adaptations (dormancy, lipid storage) are supplemented by other life strategies such as extensive vertical migrations, change in the mode of life, and trophic flexibility.