Diel and seasonal vertical distribution of meiobenthic copepods in muddy sediments of a eutrophic lagoon (fish ponds of Arcachon Bay)

The vertical distribution of meiobenthic copepods was investigated within muddy sediments of a eutrophic lagoon (fish ponds of Arcachon Bay, France). The aim of the study was to determine if in muddy sediments, as previously established in sandy sediments, meiobenthic copepods migrate vertically according to the seasons or diel periods. Two experimental approaches were used, viz: a three-season comparison was made of the diel vertical distribution of the harpacticoid Canuella perplexa T. & A. Scott (1893) and secondly the depth distribution of a meiobenthic copepod assemblage was followed for a 24 h period, in shallow water subtidal locations. The harpacticoid C. perplexa vertically migrated through the top three centimeters of the sediment, showing diel and seasonal variations in depth distribution. The differential vertical distributions shown by the dominant meiobenthic populations suggest that emergence into the water column may mainly concern surface dwelling copepods. The physical and biological factors affecting seasonal and diel changes in the copepod assemblage of the fish ponds are discussed.     

The effect of diapause emergence on the seasonal dynamics of a zooplankton assemblage

1. The role of seasonal phenology in the emergence of zooplankton from diapause in patterns of seasonal abundance in the water column was investigated in Oneida Lake, New York. Replicate emergence traps, placed in contact with the lake sediments at two locations (one at a shallow site and one at a deep site), were monitored between May and August.
2. Although six rotifer taxa showed a clear seasonal succession in the water column throughout the study period, all but one taxon emerged exclusively in spring. Three cladoceran and three calanoid copepod species, also present in the water column throughout the study period, again showed predominantly spring emergence. In contrast, three cyclopoid copepod species had distinct seasonal periods of emergence that corresponded, at least in part, to the timing of abundance peaks in the plankton.
3. These results for a single lake are largely consistent with patterns observed or inferred by other investigators for other lakes: variable dependence of abundance in the plankton on diapause emergence for species with long-lived diapausing eggs (i.e. rotifers, cladocerans and calanoid copepods), and much closer dependence for species with short-lived diapausing immature stages (i.e. cyclopoid copepods).     

Effects of a macroalgal mat (Ulva lactuca) on estuarine sand flat copepods: an experimental study

The effects of a macroalgal mat (Ulva lactuca) on intertidal sand flat copepods were studied in Jamaica Bay, NY. In 1999, Ulva was removed from paired quadrats in the algal mat. Density and species richness were estimated from sediment cores over seven biweekly periods and compared with Ulva-removal quadrats and with an unvegetated reference site. In a separate analysis at the same site, species composition and density of all copepods within the algal mat were determined from replicated quadrat samples over seven dates. Emergence traps were deployed in all treatments in 1999 to quantify copepod movements from sediments into the water column during flooding tide. Dissolved oxygen (DO) was continuously monitored over several 96-h periods in and above the algal mat. In 2000, three biomass levels of Ulva (0, 100, 200 g DW per m²) were added to paired quadrats in the unvegetated zone. Density and species richness were estimated over eight time periods. Ulva removal resulted in significant increases in density and species richness, but levels remained lower than at the unvegetated site. Likewise, addition of Ulva biomass produced significant declines in copepod density. However, the differences between low- and high-Ulva-addition treatments were insignificant. Increases in phytal copepods after Ulva addition did not compensate for losses of epibenthic and infaunal species. The overall effect of the Ulva mat was a net loss of copepod density, including the loss of nearly all infaunal species. Anoxia in sediments and within the algal mat are correlated with declines in infaunal species and with escape by some infaunal species from the sediment into the water column.     

The effect of crude oil on the colonization of meiofauna into salt marsh sediments

The effect of an oil spill on estuarine meiofauna was examined in a controlled colonization experiment. Forty-five replicate azoic sediment chambers treated with 0,133 or 381 mg hydrocarbons: 100 g dry sediment of South Louisiana crude oil were each quantitatively sampled with three replicate cores for colonizing meiofauna. Chambers were sampled on days 2, 5, 10, 30 and 60 postplacement in a Louisiana Spartina alterniflora (Loisel) salt marsh. Polychaetes showed a delayed colonization and reduced densities in oiled relative to non-oiled sediments. Nematode numbers were significantly depressed in the high oil treatment but no delay in colonization was identified. Only one species of meiobenthic copepods, Enhydrosoma woodini, displayed a reaction to the presence of the oil but only in the top centimeter of sediment. This species showed significantly decreased densities due to the heavily oiled treatment throughout the study until day 60 when numbers in the heavily oiled chambers were significantly higher than those in the non-oiled chambers. Species diversity (H') was calculated on the meiobenthic copepod assemblage and showed that diversity in the high oil treatment was generally lower than that in other treatments through day 30. Fewer species colonized the heavily oiled chambers before day 30. Principle Components Ordination conducted on the copepod assemblage could not identify an oil effect separate from a chamber effect for copepod community structure.     

Sampling demersal zooplankton: A comparison of field collections using three different emergence traps

Comparisons of demersal zooplankton collected in three structurally different emergence traps indicated that density and diversity estimates are affected by design features and sampling procedures. The smallest mesh netting (63 μm) in the walls of Hobson-Chess traps contained larger catches than traps with 202- or 333-μm mesh. Samples from Porter-Porter traps tethered 1 and 10 cm above the bottom had statistically more zooplankton than all other traps set on the substratum. A consistently greater total number of demersal zooplankton was captured in the Alldredge-King traps when all three trap types sampled at the same time and area. The abundance and rank order of all but the most numerous animals ( = harpacticoid copepods) differed between the traps. Alldredge-King traps caught more of the larger organisms (= polychaetes, cumaceans, and gammaridean amphipods), whereas, the Porter-Porter and Hobson-Chess traps contained larger densities of smaller zooplankton ( = copepod nauplii and gastropod veligers).     

Spatial scale and meiobenthic copepod recolonisation: testing the effect of disturbance size in a seagrass habitat

A central problem in relating disturbance to community structure lies in determining how community structure is affected by the size of disturbance events. In soft-bottom habitats, recovery rate and patterns of macrobenthic community are usually affected by the spatial scale of disturbance. Thus far, no studies have explicitly addressed these issues for meiobenthic copepods. To test the effects of the size of hypoxia/anoxia disturbance on the recovery of meiobenthic copepod communities in a vegetated (Ruppia cirrhosa) sediment, a field experiment was set up in Valle Smarlacca, a brackish lagoon on the northern Adriatic coast of Italy. Plots of three different sizes—small (40×40 cm), medium (80×80 cm) and large (160×160 cm)—were exposed to experimentally induced hypoxia/anoxia for 5 days. Control plots of 40×40 cm were added, for comparison with ambient abundance. Recolonisation and community recovery were then observed for 12 days, with samplings on days 0, 1, 3, 5, 7, 9 and 12. Sampling was designed to focus on the distance from source pools of colonists. The induced anoxia had a severe impact on the copepods, but the impact of the disturbance was independent of plot size. Copepod abundance increased linearly over time, and no differences in recolonisation rate among the differently sized plots were observed. Recolonisation comprised two phases: until day 3, abundances were low and very similar in all plot sizes; from day 5 onwards, abundances of the dominant species (which were the same in control and disturbed plots) increased, and a more diversified pattern among disturbance sizes was observed. Multivariate analyses showed a gradual response of community structure to disturbance size: copepod assemblages in small plots attained the same structure of the control plots at day 5, while for larger-sized plots this occurred later and was observed on the following sampling date. However, clear differences among the three disturbance sizes were never detected. Variability in community structure seemed to respond more to the overall impact of disturbance than to the size of the disturbed area. In the seagrass meadows of the Valle Smarlacca, several factors seem to influence the structural organisation of meiobenthic copepod communities during recolonisation processes. Among others, the recovery of the vegetated habitat to suitable conditions seems to play a much more relevant role than the size of the disturbed patches.     

Differential dispersal rates in an intertidal meiofauna assemblage

Meiofaunal nematodes and copepods disperse passively with sediment bedload, and copepods also display active emergence and reentry behavior. Epigrowth-feeders may be the nematode feeding group most susceptible to passive transport because they live closest to the sediment surface. We used bottom traps at a nematode-dominated intertidal mudflat in Maine, USA, to test the hypotheses that (1) meiofauna taxa disperse in relative proportions different from those of the ambient community; (2) copepods have the highest relative dispersal rate (number of individuals trap⁻¹ day⁻¹ ambient individual⁻¹) and are not as tightly linked as other taxa to sediment flux; and (3) epigrowth-feeders have the highest nematode relative dispersal rate. Results supported all three hypotheses. Nematodes accounted for 95.8% of the individuals in cores, but only 38.9% of the individuals in traps. Copepods accounted for 1.5% of the individuals in cores, but 56.7% of the individuals in traps. Less common taxa also had different relative proportions in cores and traps, as did nematode feeding groups and individual species. The relative dispersal rate was far higher for copepods than for any other taxonomic group, and the absolute (number of individuals trap⁻¹ day⁻¹) and bulk (number of individuals g sediment⁻¹ trap⁻¹ day⁻¹) dispersal rates for copepods were equal to those of the 65-fold more abundant nematodes and higher than those for all other taxa. The non-selective deposit-feeders were the most abundant nematode feeding group in the ambient community, but the epigrowth-feeders as a group and as individual species had the highest absolute, relative, and bulk dispersal rates. Non-metric multidimensional scaling (MDS) using analysis of similarity (ANOSIM) and species similarity percentages (SIMPER) reflected these differences between ambient and dispersing nematode assemblages. Significant positive regression relationships between sediment weight and the number of individuals captured in traps for nematodes and some other taxa indicated that they moved passively in the bedload. Lack of a significant regression relationship for copepods suggested an active behavioral component to dispersal. Meiofauna populations in this soft-bottom community were highly dynamic, demonstrating that the role of dispersal must be included in any consideration of the ecology of soft-bottom systems at local and regional spatial scales.     

Seasonal abundance, reproduction and development of four key copepod species on the Faroe shelf

The copepod community on the Faroe shelf is dominated by Calanus finmarchicus, Temora longicornis, Acartia longiremis and Pseudocalanus spp. The species composition, abundance and development of the copepod community varied considerably during the season 2004. These variations reflected to a large extent the different life strategies of the copepods. Both nauplii and copepodites of C. finmarchicus were most abundant during spring and early summer. The two neritic copepods T. longicornis and A. longiremis were present in low numbers during spring but dominated the copepod community later during the productive period. Pseudocalanus spp., on the other hand, occurred throughout the year, but showed no clear numerical response in abundance to the spring bloom. The egg production measurements of C. finmarchicus and T. longicornis showed some pre-bloom egg production, but as the spring bloom started the egg production rate increased significantly, especially for C. finmarchicus. There seemed to be a substantial loss of nauplii and copepods from the shelf ecosystem during the productive season. It was, however, not possible to determine whether this was mainly due to mortality or advective loss.     

拓林湾浮游桡足类生态研究

2000年7月至2001年7月的周年调查结果表明,粤东柘林湾浮游桡足类29属57种,其中,强额拟哲水蚤Paracalanus crassirostris和短角长腹剑水蚤Oithona brevicornis为优势种,合计占浮游桡足类总个体数的66.7%.柘林湾是一个浮游桡足类相对丰富的海湾,年均总个体数达5.4×10³ind.·m^-3.浮游桡足类的种类数和总个体数均表现为湾外大于湾内的平面分布格局,周年变化基本上为单峰型,高峰期位于5~10月,最低谷位于冬季1月。     

海南岛西北沿岸海域浮游桡足类的分布及群落特征

为了解昌江沿岸海域生态系统的现状, 探讨海域环境因素对浮游动物的生存环境造成的影响。本文根据2008年11月至2009年7月在海南西部昌江沿岸水域21个测站、4个季度月调查所获的浮游桡足类样品数据, 对该海域浮游桡足类群落结构、分布、季节变化及影响因素进行了分析。本调查共鉴定出桡足类44种, 隶属4目17科24属, 其中秋季25种, 冬季23种, 春季22种, 夏季23种。本次调查共发现优势种6种, 分别是微刺哲水蚤(Canthocalanus pauper)、亚强次真哲水蚤(Subeucalanus subcrassus)、锥形宽水蚤(Temora turbinata)、刺尾纺锤水蚤(Acartia spinicauda)、椭形长足水蚤(Calanopia elliptica)和精致真刺水蚤(Euchaeta concinna), 优势种以近岸暖水种居多。浮游桡足类丰度季节变化明显: 冬季最高, 达409 ind./m³; 秋季次之, 为144 ind./m³, 春季为55 ind./m³, 夏季最低仅为17 ind./m³。其丰度的平面分布显示: 秋、冬季节分别在海区中部和南部形成明显密集区, 春、夏季节则大致呈现由外海向近岸逐渐递减的趋势。浮游桡足类的多样性指数(H')表现为夏季>春季>秋季>冬季, 春、夏季的均匀度指数(J')明显高于秋、冬季。本调查反映出该海区的桡足类群落具有热带—亚热带区系特征, 种类组成季节更替明显, 桡足类种群受海域水温和硅藻的影响明显, 受盐度影响不明显。     

Mixtures of metals and hydrocarbons elicit complex responses by a benthic invertebrate community

A microcosm experiment was used to examine the effects of co-contamination with environmentally realistic but relatively low concentrations (expected to cause occasional to frequent adverse effects) of diesel fuel and metals (Cu, Cd, Hg, Cr, and Pb) on a saltmarsh benthic invertebrate community. After 30 days, exposure to metals did not influence abundances of major meiofaunal taxa (nematodes, ostracods, total copepods, nauplii, or chironomid larvae) or individual copepod species. Diesel exposure did not influence nematode or total copepod abundances, but significantly decreased abundances of ostracods, nauplii, and chironomids. For all taxa except copepods, the metals+diesel treatment yielded results similar to the effects of diesel alone. Although total copepod abundances were not significantly influenced by metals- or diesel-only treatments, abundances were significantly reduced in the metals+diesel treatment, a response that appeared consistent with a non-additive toxicological synergism between metals and diesel. Responses of copepod species to the diesel-only treatment were varied; species could be categorized as ‘diesel-sensitive’ (declined in abundance, presumably due to direct (toxic) effects), or ‘diesel-resistant’ (abundance either unchanged, or increased due to indirect (ecological) effects). In the metals+diesel treatment, the effects on ‘diesel-sensitive’ species were similar to those observed in the diesel-only treatment. However, abundances of ‘diesel-resistant’ species declined in the metals+diesel treatment, suggesting that metals interfere with the indirect effects that lead to enhanced abundances of some species and/or that metal+diesel combinations are uniquely toxic. Collectively, however, responses of most individual copepod species to metals+diesel suggested an additive toxicological action, and thus differed from the apparent synergism observed for total copepod abundance. The presence of diesel enhanced the retention of metals in sediments, which may have important toxicological implications. We conclude that, at relatively low concentrations of metal and diesel fuel co-contamination, both direct (toxic) and indirect effects influence faunal abundance; thus, reductions in abundance of major taxa may give the appearance of toxicological synergisms that are not manifested at the species level.     

Effects of moonlight on the vertical migration patterns of demersal zooplankton

The diel vertical migration patterns of demersal zooplankton, those organisms which habit bottom substrates but periodically emerge to swim freely in the water column, water determined throughout the lunar cycle. Demersal zooplankton were quantitatively sampled on a subtidal sand flat in the Gulf of California every 2 h for 24-h periods at new, full, first, and last-quarter moons, both as they emerged into the water column and as they returned to the benthos. Demersal zooplankton rarely migrated during daylight. Three general patterns of migration were observed. (1) Polychaetes and cumaceans emerged from the benthos at dusk, regardless of the phase of the moon. Polychaetes returned to the benthos throughout the night while cumaceans returned near dawn. (2) Species of amphipods and isopods exhibited significant avoidance of moonlight, delaying emergence until moonset or returning to the benthos at moonrise. (3) Species of copepods, mysids, shrimp, Branchiostoma (cephalochordate), and tanaids emerged into the water column throughout the night. The timing of migration was highly variable and did not correlate with the presence or absence of moonlight. Large zooplankton migrated less frequently into the water column during moonlit periods than small forms, suggesting that nocturnal predation by visually oriented planktivorous fish may be an important selective pressure.Demersal zooplankton emerged into artificially darkened emergence traps in significantly higher numbers during daylight and during full and quarter moons than into undarkened control traps, demonstrating that absence of light is a major cue stimulating migration. Reentry traps resting on the bottom captured higher densities of demersal zooplankton than either emergence traps or reentry traps suspended off the bottom. Thus, many demersal zooplankton remain near the bottom, rarely swimming far into the water column. Some trap avoidance was observed and current methods for collecting demersal zooplankton are evaluated. Since most demersal zooplankton remained in the water column only a short time, dispersal, particularly over short distances, may be a major advantage of migratory behavior. Migration facilitates rapid recolonization of disturbed or defaunated sites, disrupts and mixes bottom sediments, and results in daily variation in the microdistribution, patchiness, and species composition of the benthic fauna.     

Intrashoot distributions of leaf dwelling harpacticoid copepods on the seagrass Zostera marina L.: implications for sampling design

The distribution of leaf dwelling harpacticoid copepods within seagrass (Zostera marina L.) shoots was investigated on four dates in 1986 and 1987. Copepods were found to be non-uniformly distributed on shoots, with higher abundances observed on older leaves. Patterns of abundance within shoots could not be explained by the surface area of individual leaves except on the sampling date with the highest copepod densities. It is suggested that harpacticoid copepod distributions on seagrass shoots are primarily determined by the pattern of epiphytic biomass. However, at high population densities, habitable surface area may be the limiting factor. Increased habitat complexity at high epiphyte loads does not seem to be the cause of the copepod distributions observed in this study. An accurate method for estimating seagrass copepod abundance per unit sediment area using intrashoot distributions is described and compared to existing methodology.     

Distribution and habitat preferences of species within the genus Elaphoidella Chappuis, 1929 (Crustacea: Copepoda: Harpacticoida) in Slovenia

Twelve species of the harpacticoid genus Elaphoidella, most of them exclusively groundwater species, have been recorded in Slovenia (SE Europe). Their distribution and ecology are reviewed with the aim of evaluating distribution patterns, species preferences for groundwater habitats, ecological preferences and interactions with other copepod species at regional scale. Data on Elaphoidella species were obtained partly from the existing literature and partly from the author's (AB) own sampling campaigns carried out together with his co-workers. During the rich history of collecting copepods in Slovenia (from the 1920s to present), Elaphoidella species were recorded at 78 sampling sites altogether. The majority of collecting was conducted in the southern (Dinaric region) and north-western (Alpine region) Slovenia. The most intensively sampled habitats were porous aquifers of alluvial plains, springs in the karstic unsaturated zone and percolation water in caves. The highest species richness of Elaphoidella was recorded in the southern Slovenia, where 10 species were found. The strictly “Dinaric” species are E. charon, E. franci, E. karstica, E. stammeri, E. sp. 1 and E. sp. 2, while E. phreatica and E. bidens were found exclusively in the north-western Slovenia. From the latest data on the copepod distributions (2002–2004), where the environmental characteristics of sampling sites were also measured, the relationship between selected environmental characteristics of the habitats and the presence of Elaphoidella species was analysed. The distribution of Elaphoidella species in Slovenia was found to be related with the region, habitat type, altitude, conductivity and pH of the water.     

Invertebrate dispersal and habitat heterogeneity: Expression of biological traits in a seagrass landscape

Seagrass meadows harbour diverse faunal assemblages, but the relative importance of landscapes attributes, settlement processes and biological traits of individual species for recruitment patterns is poorly understood. To quantify the influence of habitat heterogeneity on larval, juvenile and adult post-larval dispersal, invertebrates (> 125 µm) were collected in benthic settlement traps at five occasions (June-August) in three habitats; continuous seagrass, seagrass patches and bare sand. The study was carried out by SCUBA diving in a subtidal (2.5 m depth) seagrass landscape dominated by Zostera marina L. in the Baltic Sea. Traps collected totally > 30 taxa, with non-significant effects of habitat on species richness and total abundance. Total number of invertebrates exhibited strong temporal variability, probably driven by wind-induced bedload and water column transport. Surprisingly, traps located in small (< 12 m²) patches contained on average almost twice as many individuals as traps located in the continuous vegetation. Dominating taxa such as nematodes, copepods, and oligochaetes were found in similar densities across the landscape. In contrast, location within the landscape had strong effects on bivalve settlement and redistribution patterns, resulting in significantly lower densities in continuous vegetation compared to patches and bare sand. A biological trait analysis indicated that semi-mobile taxa with annual protracted direct development, and short-distance dispersal are probably of higher importance for the community assembly process in this environment than long-distance larval dispersal. Results suggest that seagrass landscapes are highly dynamic environments, characterized by time and species-specific effects of landscape attributes on animal dispersal and recruitment. A conceptual model illustrating interactions between settling larvae and landscape heterogeneity is presented.     

Drifting Algae as a means of Re-Colonizing Defaunated Sediments in the Baltic Sea. A Short-Term Microcosm Study

We conducted a microcosm experiment to evaluate the capability of fauna inhabiting or being transported by drifting filamentous algae to colonize defaunated sediment. We expected meiofauna would perform a quicker and more effective re-colonization of disturbed areas by means of the algal mats than their macrofaunal counterparts. Similarly, within meiofauna, we expected more mobile taxa such as ostracods and harpacticoids to colonize the sediment more readily than other more sedentary ones such as nematodes. Naturally drifting algae were collected from the field and placed in 1 l aquaria on top of 5 cm of defaunated sediment. After 3 and 6 days, one core sample (5 cm deep) was taken from each aquarium; the first 2 cm were sliced into 2 mm layers, and the remaining fraction into 1 cm layers. The sediment remaining in the aquaria was sieved through a 0.5 mm sieve to collect the re-colonizing macrofauna. The dominant macrofaunal taxa inhabiting the algae were juvenile bivalves and gastropods, with Cerastoderma glaucum accounting for the majority of the bivalves and Hydrobia sp. for most of the gastropods. After 3 and 6 days, the most abundant macrofaunal taxa colonizing the sediment were Cerastoderma glaucum, Hydrobia sp. and gammarid amphipods. Higher abundances were found after 6 days than after 3, though differences were not significant for any of the major taxa. Meiofauna inhabiting the algae were dominated by rotifers, nematodes, ostracods, chironomid larvae and harpacticoid copepods. Contrary to our predictions, nematode and harpacticoid species inhabiting the drifting algae were not driven to sediment re-colonization but remained in the algae. Our results indicate that some benthic animals may indeed benefit from drifting algal mats as a means of dispersal and re-colonization of previously defaunated sediments in relatively short periods of time. Also, they may contribute to explain some of the trends found in other studies, regarding species increase under drifting algae and the recovery patterns found in areas often exposed to algal conglomerates.     

Distribution of seagrasses along the Indian coast

Seagrass environments, from the main coast of India, Lakshadweep and Andaman Islands, were surveyed for seagrass and marine algal composition. Extensive seagrass meadows and the maximum number of species (seven genera and 12 species) occurred along the Tamil Nadu coast. Seagrasses were observed from intertidal to subtidal regions down to 8 m depth. Thalassia hemprichii (Ehrenberg) Aschers. and Cymodocea serrulata (R. Brown) Aschers. & Magnus were the dominant seagrasses in the subtidal zones. Halophila beccarii Aschers. was restricted to the intertidal mudflats in association with mangroves. The rich growth of seagrasses along the Tamil Nadu coast and Lakshadweep can be attributed mainly to high salinity, clarity of the water and sandy substratum. One hundred species of marine algae were recorded from the seagrass environments of India.     

Interactions between Benthic Copepods,Bacteria and Diatoms Promote Nitrogen Retention in Intertidal Marine Sediments

The present study aims at evaluating the impact of diatoms and copepods on microbial processes mediating nitrate removal in fine-grained intertidal sediments. More specifically, we studied the interactions between copepods, diatoms and bacteria in relation to their effects on nitrate reduction and denitrification. Microcosms containing defaunated marine sediments were subjected to different treatments: an excess of nitrate, copepods, diatoms (Navicula sp.), a combination of copepods and diatoms, and spent medium from copepods. The microcosms were incubated for seven and a half days, after which nutrient concentrations and denitrification potential were measured. Ammonium concentrations were highest in the treatments with copepods or their spent medium, whilst denitrification potential was lowest in these treatments, suggesting that copepods enhance dissimilatory nitrate reduction to ammonium over denitrification. We hypothesize that this is an indirect effect, by providing extra carbon for the bacterial community through the copepods'' excretion products, thus changing the C/N ratio in favour of dissimilatory nitrate reduction. Diatoms alone had no effect on the nitrogen fluxes, but they did enhance the effect of copepods, possibly by influencing the quantity and quality of the copepods'' excretion products. Our results show that small-scale biological interactions between bacteria, copepods and diatoms can have an important impact on denitrification and hence sediment nitrogen fluxes.     

Planktonic marine copepods and harmful algae

Marine planktonic copepods are important grazers on harmful algae (HA) species of phytoplankton, and copepods are major entry points for vectorial intoxication of pelagic food webs with HA toxins. Previous reviews (Turner and Tester, 1997, Turner et al., 1998a, Turner, 2006) summarized information on HA interactions with zooplankton grazers, and vectorial intoxication of pelagic food webs, up through approximately 2005. Accordingly, this review will address primarily studies published during the last decade. It will concentrate on generic issues in the developing field of HA:grazer interactions, such as the extent to which HA toxins serve as copepod grazing deterrents, induction of HA grazing deterrents by exposure to copepods, copepod selective feeding to avoid ingesting HA taxa versus non-selective feeding on HA taxa, possible biogeographic aspects of the effects of HA toxins on copepods, impact of copepod grazing on HA bloom development and termination, the role of copepods as entry points for vectorial intoxication of pelagic food webs with HA toxins, and possible reasons and remedies for the highly-variable and conflicting results reported for many studies of copepod grazing on various HA species.     

Peritrich epibiont protozoans in the zooplankton of a subtropical shallow aquatic ecosystem (Monjolinho Reservoir, Sao Carlos, Brazil)

Peritrich epibiont protozoans and metazooplankton (rotifers,cladocerans and copepods) were investigated seasonally in ashallow eutrophic artificial reservoir in a subtropical region(Monjolinho Reservoir, Brazil). The ciliated peritrichs Rhabdostylasp. and Scyphidia sp. were found to colonize individuals ofdifferent metazooplanktonic groups, especially copepods (47.20%of the total number of metazooplanktonic organisms found withepibionts and 57.14% of infection in the copepod population).Copepods also had the greatest epibiont load, followed by cladoceransand rotifers. Rotifers were the most important metazooplanktonicgroup (90.14% of the total) and the taxa observed with epibiontswere Filinia longiseta, Polyarthra, Brachionus and Keratella,with highest preference for the first organism. F. longisetawas present at low density compared with the others and thepreference as a substrate for epibionts may be related to itstype of adhesion surface (soft) and/or feeding habits (particlefeeding).