A new species of Acartia (Copepoda, Calanoida) from the Yellow Sea

A new species (Acartia hongi) of Acartia (family Acartiidae)predominating in the Korean coastal waters of the Yellow Seais described. This species closely resembles Acartia bifilosa,from which it can be easily distinguished by the co-occurrenceof the following morphological characters: the absence of rostralfilaments in both genders; the terminal spine on the femalefifth leg toothed only on the inner side; the first exopodalsegment of the male right fifth leg with a long seta; the distalsegment of the male left fifth leg with a rod-like appendage.Its distribution was discussed in comparison with two siblingspecies, Acartia omorii and Acartia hudsonica.     

Egg production of individual copepods of Acartia grani Sars from coastal waters: seasonal and diel variability

Seasonal and diel fecundity patterns of adult Acartia granifemales from a coastal area of Malaga Bay (south of Spain) werestudied between spring and autumn 1990. Copepod egg productionwas measured in situ by short-term (     

Plankton distribution across a slope current-induced front in the southern Bay of Biscay

Relatively warm (12.50–12.75°C) and high-salinity[<35.640 practical salinity units (PSU)] water flowing eastwardwas detected at the shelf-break during a cruise carried Outin the southern Bay of Biscay in Spring 1987. The slope currentinduced the formation of a convergent front separating well-mixedoceanic waters from haline-stratified coastal waters. Very highconcentrations of dissolved oxygen (295 µmol kg^–1)and chlorophyll a(>4.5 mg m^–3) were found at the outeredge of the frontal boundary. Small autotrophic flagellatesdominated the phytoplankton community. Primary production peakedat the boundary region. Estimated phytoplankton growth ratesindicated that active growth was taking place, with lower turnovertimes integrated over the water column at the frontal station(2.5–5 days) than at coastal (1.5–2.8 days) or oceanic(1.5–3.5 days) stations. The lowest doubling times (1–2days) were calculated for surface frontal populations. Accumulationof zooplankton was also observed associated with the convergentphysical structure, although this relationship was less markedthan for phytoplankton. Copepods, mainly Paracalanus parvus,Acartia clausi and Oithona helgolandica, formed the bulk ofthe mesozooplankton biomass. Compatibility between the sizeof phytoplankton cells and copepod size spectra indicate highfood availability for these animals, particularly in the vicinityof the front. The distribution of fish eggs and fish larvaewas also coupled with the slope current-induced front. Sardinelarvae were more abundant at the coastal side of the front,whereas larval stages of blue whiting reached the highest densitiesat off-shelf stations. Larvae of lamellibranch molluscs andbryozoa were restricted to nearshore waters, as the frontalboundary prevented larval dispersion to the open ocean. Theresults presented in this paper suggest that the Iberian slopecurrent and its associated shelf-break frontal structure werecrucial in controlling phytoplankton primary production, activityof grazers, distribution of larvae of fishes and benthic invertebrates,and ultimately in determining the structure of the pelagic foodweb in the southern Bay of Biscay during the seasonal periodof vertical mixing.     

Copepod and barnacle nauplius distributions in the Irish Sea: relation to springtime hydrographic variability

The distributions and abundances of copepod and barnacle naupliiare described along a five-station transect in the Irish Seafrom Liverpool Bay, England, to Dundalk Bay, Ireland, in May1989. Correspondence analysis revealed that various hydrographicregions in the Irish Sea are characterized by distinct naupliusassemblages. Acartia, Centropages and Temora nauplii were associatedwith the Welsh coastal water east of the Liverpool Bay front.The western stratified water to the west of the seasonal, westernIrish Sea front was distinguished from the mixed water to theeast by abundances of Calanus, Pseudocalanus, Oithona, Microcalanusand harpacticoid nauplii. The Liverpool Bay and western IrishSea fronts are, apparently, boundaries between coastal and offshoreassemblages of crustacean nauplii.     

A simulation of the distribution of Acartia clausi during Oregon Upwelling, August 1973

The distribution of the estuarine copepod Acartia clausi incoastal waters off Oregon during an upwelling period in August1973 is simulated. A time dependent, two dimensional (x, z,t) model relates maximum offshore extent of the copepod's fourlife stages (egg, nauplius, copepodite, and adult) to intensityof the wind stress driving the upwelling circulation, stagedevelopment time, and mortality. Realistic solutions are obtainedby using actual intermittent wind forcing recorded by an anemometerat Newport. Offshore transport is overestimated when the circulationmodel is driven by theoretical continuous winds, suggestingzooplankton may be washed out of coastal upwelling zones (e.g.off Northwest Africa) which undergo periods of prolonged upwelling. With an accurate model of offshore transport and stage developmenttime, the mismatch between predicted and observed distributionsmay be used to estimate field mortality of the various stages.     

Copepod populations during the spring bloom in an Alaskan subarctic embayment

Copepod population and biomass was monitored in Auke Bay, Alaska,during the spring bloom from 1987 to 1989. The most abundantspecies were Pseudocalanus spp., Oithona similis and Centropagesabdominalis, with Acartia clausi reaching high concentrationsin the surface waters. Although populations of Pseudocalanuswere similar during all three years, C.abdominalis and O.similisconcentrations were significantly higher in 1988 and lower in1989 than in 1987. The population differences may have resultedfrom warmer temperatures during early spring in 1988. Substantialcontributions to biomass resulted from advection of adult Calanusmarshallae and Metridia ochotensis and late stage Neocalanusplumchrus into the bay. While copepod populations in Auke Bayappear to be more sensitive to factors influencing the timingand development rate of various cohorts, biomass is substantiallyaltered by water mass movements.     

Distribution and dietary relationships of the Japanese temperate bass Lateolabrax japonicus juveniles with two contrasting copepod assemblages in estuarine nursery grounds in the Ariake Sea, Japan

Early juvenile Japanese temperate bass Lateolabrax japonicus samples were collected during four cruises to study the spatial and temporal patterns of distribution and feeding habits of the fish in Chikugo estuary, Ariake Sea, Japan. Gut contents were studied by separating, identifying and counting the prey organisms. Plankton samples were collected during each cruise to study the numerical abundance of copepods in the water. Copepod dry biomass and gut content dry mass were estimated. Juveniles were distributed over wide estuarine areas in salinities ranging from as low as 0·37 to as high as 28·81. Considerable spatial and temporal variations were observed in the copepod distribution in the environment and in the food habits of the fish. Two distinctly different copepod assemblages were identified along the estuary: one in the upper river, dominated by a single species Sinocalanus sinensis, and the other a multi‐specific assemblage in the lower estuary dominated by common coastal copepods such as Acartia omorii, Oithona davisae, Paracalanus parvus and Calanus sinicus. The gut content composition corresponded strongly with the copepod composition in the environment, i.e. a single species (S. sinensis) dietary habit at the upper river and a multi‐specific dietary habit dominated by the common coastal copepods in the lower estuary. Ivlev's electivity index showed that the fish strongly preferred larger copepods and avoided smaller ones. Higher dry biomass of copepods in the water as well as higher dry masses of the gut contents were recorded in the low‐to‐medium saline upper river areas, indicating that these areas are of particular importance as nursery grounds for the juvenile Japanese temperate bass. It was speculated that ascending to the upstream nursery areas to utilize S. sinensis, which is the single dominant copepod in these areas, is one of the most important survival strategies of the Japanese temperate bass juveniles in the Chikugo estuary.     

Productivity, photosynthetic pigments and hydrology in the coastal front of the Eastern English Channel

In the French area of the Eastern English Channel, the coastalwaters 3 or 4 miles wide are separated from offshore watersby a coastal front. The phytoplanktonic biomass (B) and production(P) are higher in coastal waters, and an increase of biomasshas been observed at the interface. This frontal biomass, lessproductive, resulted from hydrodynamic accumulation, not dueto local growth. The productivity (P/B) deficit (50%) spreadsover the external area of the front, probably because the biomassis partly constituted of exported inactive coastal phytoplankton.The productivity is higher again in offshore waters. The variationof the pigment pool indicates a stress on phytoplankton in thefront and this ergocline was not productive at the time of thetwo cruises.     

Seasonal variability of phytoplankton populations in the middle Adriatic sub-basin

The seasonal variability of phytoplankton assemblages in themiddle Adriatic sub-basin is described. The investigated areacrossed the middle Adriatic from the Italian to the Croatiancoasts. Hydrographic data, chlorophyll (Chl) a and phytoplanktonwere collected on a seasonal basis from May 1995 to February1996. Highest phytoplankton densities (up to 6 x 10⁶ cells dm^–3)were observed in spring and autumn in the western side, withinthe diluted waters. The vertical distribution of Chl a exhibiteda pronounced subsurface maximum associated, in coastal waters,with micro-planktonic diatoms. Phytoplankton assemblages weredominated by phytoflagellates in all the periods investigated.Diatom maxima were observed in spring and autumn: their verticaldistribution generally reflected the Chl a pattern and in thewestern coastal area peaks are due to large diatom species (Pseudo-nitzschiaspp.). In offshore waters, dinoflagellates strongly prevailover diatoms and provide a relevant contribution to the totalbiomass, especially in highly stratified conditions. Coccolithophoridswere mostly encountered in surface layers and their highestcontribution to the total biomass was observed in the LevantineIntermediate Water.     

New mysids from the South Australian coastal waters: Paranchialina secunda sp. nov.; Leptomysis longisquama sp. nov. and Doxomysis johnsoni sp. nov.

Three new species are described, Paranchialina secunda. Leptomysislongisquama and Doxomysis johnsoni from the coastal waters ofSouth West Australia.     

Population genetics of drifting (Calanus spp.) and resident (Acartia clausi) plankton in Norwegian fjords

Kaartvedt distinguished between drifting and resident planktonand hypothesized that the latter were distinguished by theirability to maintain their horizontal position in desired habitats(Kaartvedt, 1993). In this study, we examined the populationgenetic consequences of these two lifestyles for copepods infour fjords of western Norway (Lurefjorden, Masfjorden, Sognefjordenand Sørfjorden) and one fjord in eastern Norway (Oslofjorden).Based on DNA sequence variation of a region of mitochondrial16S rRNA, we contrasted population genetic diversity and structurein drifting populations of Calanus spp. with that of residentpopulations of Acartia clausi. With the exception of Sørfjorden(where Calanus spp. were rare), two or three species of Calanusco-occurred in significantly different proportions in the fjords.Based on a 350 base-pair region of mitochondrial 16S rRNA, Calanusspp. varied in molecular genetic diversity, with the highestvalues for C.helgolandicus. There was no evidence of significantgenetic structure of fjord populations for either C.finmarchicusor C.helgolandicus; the population structure of C.glacialiscould not be evaluated as the species was only abundant in Lurefjorden.Acartia clausi was abundant in all five fjords sampled for thisstudy. Molecular genetic diversity of A.clausi, based on a 220bp region of mt 16S rRNA, was within the range of Calanus spp.values. Populations of A.clausi showed significant genetic structure(i.e. haplotype frequencies differed markedly) among the fjords.The results of this study indicated that little exchange (geneflow) occurs between populations of A.clausi in different fjords,and suggested that the populations are long-term residents ofa fjord. In contrast, most Calanus spp. fjord populations maybe replaced periodically, as they drift with currents flowingto and from coastal and fjord environments.     

Zooplankton diversity and the predatory impact by larval and small juvenile fish at the Fisher Banks in the North Sea

The biomass and diversity of the mesozooplankton and fish larvaecommunity were investigated across a frontal zone in the centralNorth Sea in the early summer, to investigate whether larvalfish predation is a regulator of mesozooplankton production.Pronounced changes in the mesozooplankton community were observedacross the front off the Jutlandic coast. The biomass and thediversity of copepods changed across the front as the populationof Calanus finmarchicus became abundant in the deeper water.The crustaceans (Acartia spp. and Evadne spp.) and polychaetelarvae dominated the mesozooplankton in the coastal water. Thebiomass of fish larvae was dominated by gadoid larvae. As inthe copepods, a shift in fish diversity was observed in thefrontal zone. On the coastal side of the front, whiting (Merlangiusmerlangus) dominated the biomass, while offshore from the frontwhiting were absent and cod (Gadus morhua) was the dominantlarval fish species on the deeper stations. The present investigationdemonstrates two different trophic pathways related to hydrographyin the central North Sea. First, in the shallow coastal water,the abundant small neritic copepods are predominately predatedby whiting, while in the offshore region the larger oceaniccopepods are predated by cod larvae. However, the predationpressure by the fish larvae was in general low (<10%) relativeto copepod production per day. Consequently, in the early summer,the copepod production potentially results in a build-up ofcopepod biomass on both sides of the front.     

Description of the developmental stages in Acartia bifilosa Giesbrecht (Copepoda: Calanoida)

The developmental stages and increase in length of Acartia bifilosa,a dominant planktonic copepod in Kyeonggi Bay, Yellow Sea, Korea,were investigated in a laboratory. Adults laid eggs at a rateof 2.5 eggs day^–1 female^–1 and up to 97% of eggshatched. The eggs were 92 µm in diameter and larger thanthe eggs of other Acartia species. The body segmentation wasrecognizable at the fifth nauplius stage and sex distinctionwas possible at the fourth copepodite stage. Thesix naupliusstages took -7.5 days and the five copepodite stages -8.5 days.Sexually mature males and females appeared at the 16th day,and by the 20th day the adults laid eggs that hatched and grewsuccessfully into the nauplius stages. The detailed morphologicalcharacteristics of each developmental stage are presented anddiscussed in relation to A.dausi.     

The copepod Centropages abdominalis as a carrier of the stalked ciliate Zoothamnium

Adult specimens of the calanoid copepod Centropages abdominalis collected from February through April 1986 in Shinhamako, a saline lake connected to Tokyo Bay, were heavily infested with the stalked ciliate Zoothamnium. The number of copepods and those infested varied during the infestation period; in February when the copepod population was large, the incidence of infestation was low, whereas in March when the copepod population was small, copepods infested with Zoothamnium were proportionally more abundant. Numerical variations of infested copepods may correspond to changes in the Zoothamnium population. No specimens of Acartia omorii, which coexists with C. abdominalis, were infested in 1986, although a small number of A. omorii were infested with peritrich ciliates in 1985. Some shrimp larvae were also covered with the same peritrichs as copepods. Nevertheless, as a whole, the relationship between the phoront and its carrier seems to be specific. The highest incidence of infested copepods was approximately 30% similar to that in 1985. The sex ratio of C. abdominalis changed on each sampling date but in general females were more numerous than males. The percentage of infested males was higher than that of infested females, suggesting that the former can be attached to more easily than the latter.     

Sublethal effects of cupric ion activity on the phototaxis of three calanoid copepods

Using wavelengths near maximal photosensitivity, phototactic responses of two estuarine calanoid copepods (Acartia tonsa, Acartia hudsonica) and one nearshore, neritic copepod (Temora longicornis) were measured after 24 h exposures to sublethal concentrations of free cupric ions. A nitrilotriacetate-trace metal ion buffer system was used to control the free cupric ion activity (pCu = negative log of the free cupric ion activity), which determines organismic response. All three species exhibited positive phototaxis at pCu 13.0 reported for unpolluted surface sea waters and estuarine waters. As cupric ion activity increased, percent positive phototactic response decreased, indicating a strong sublethal effect of free cupric ions on photobehavior. Changes in photobehavior occurred at cupric ion activities that have been reported for many estuaries and coastal waters near urban and industrialized areas. Temora longicornis was much less phototactically sensitive than the two estuarine species. It also exhibited phototactic sign switching as pCu changed.     

Mesozooplankton grazing under conditions of extreme eutrophication in Guanabara Bay, Brazil

The objective of the present study was to quantify mesozooplanktongrazing in the eutrophic waters of Guanabara Bay. Mesozooplankton(>200 µm) was dominated by the copepods Acartia lilljeborgi,Acartia tonsa, Parvocalanus crassirostris and Paracalanus furcatus.Dinoflagellates, specifically the species Prorocentrum triestinum,were an important group for mesozooplankton nutrition, beingingested in significant amounts during all experiments. On average,12.3 ± 2.9 P. triestinum cells were ingested copepod^–1min^–1 (other dinoflagellates: 11 ± 8 cells copepod^–1min^–1). Filamentous cyanophyceae and nanoplankton wereingested in one experiment each, but the mesozooplankton communitygenerally preferred dinoflagellates to these groups, which werealways abundant in the water column. Euglenophyceae were notingested, although they dominated in one experiment. Mesozooplanktoningested, on average, only 0.2% of the nano- and microplanktonbiomass per day. The results suggest that grazing was not acontrolling process for the nano- and microplankton communityin the study area. Addition of zoeae larvae of Chasmagnatusgranulata (Decapoda: Brachyura: Grapsidae) in one experimenthad a significant effect on the mortality of adult copepods,probably due to a predator–prey relationship.     

Picoplankton community structure at a coastal front region in the northern part of the South China Sea

Abundances of picoplankton groups were determined by flow cytometryin the Northern South China Sea (SCS) in winter 2004 to studythe dynamics of picoplankton at a coastal front region. Prochlorococcusis more abundant in relatively high temperature and salinitywaters than in nearshore area. Heterotrophic bacteria dominatein total picoplanktonic biomass but keep rather stable in biomassand surface/bottom biomass ratio on both sides of the front.Increases of picophytoplanktonic biomass and their surface/bottombiomass ratio are remarkable mainly owing to the contributionof Synechococcus on the offshore open SCS waters. Temperatureis found to limit the growth of Synechococcus and Prochlorococcus.Picoeukaryotes and heterotrophic bacteria are less sensitiveto the change in hydrographic conditions across the front. Theautotrophic/heterotrophic biomass ratio of picoplankton is lowerin eutrophic coastal waters on the nearshore side relative tothe offshore and oligotrophic open SCS.     

Effects of small-scale turbulence on development time and growth of Acartia grani (Copepoda: Calanoida)

To test the effects of small-scale turbulence on developmentand growth of marine copepods, a series of 10 1 labortory microcosmswere used to follow the development, under turbulent and calmconditions, of a cohort of Acartia grani, a common coastal planktoniccopepod of temperate zones Aside from possible indirect effectsdue to differences in food availability, turbulence significantlyshortened development times and modified growth rates Theseinfluences seem to vary throughout its life history, late naupliiand early copepodites being more affected.     

The China Coastal Current as a driving force for transporting Calanus sinicus (Copepoda: Calanoida) from its population centers to waters off Taiwan and Hong Kong during the winter northeast monsoon period

Calanus sinicus is a copepod with wide geographical distributionin the continental shelf waters of China. Its occurrence inoceans around Taiwan and Hong Kong is limited by temperatureto winter and spring. We present evidence to show that C. sinicusis carried into the coastal waters of Taiwan and Hong Kong frompopulation centers in the Yellow Sea and the East China Seaby the China Coastal Current during the northeast monsoon periodin winter.     

Toxicity of coastal coccolithophores (Prymnesiophyceae, Haptophyta)

Over the last decade, certain coccolithophores have been thesubject of extensive multidisciplinary research. Several speciesof coccolithophore, belonging mainly to the families Pleurochrysidaceaeand Hymenomonadaceae, inhabit inshore coastal waters where theymay occasionally bloom and hence impact aquaculture resources.The toxicity to Artemia salina larvae of 11 species of coccolithophore(nine coastal and two oceanic members of the order Coccolithales)was tested. For the nine coastal species, tests were conductedwith rapidly growing and stationary phase cultures at a rangeof cellular concentrations and for two different exposure times(24 and 48 h). Five of the coastal species (four in the genusPleurochrysis as well as Jomonlithus littoralis) were foundto be toxic to A. salina nauplii. Allelopathic effects of acell-free filtrate of a culture of a toxic coccolithophore werealso tested on three flagellate microalgal species: Scrippsiellatrochoidea, Tetraselmis sp. and Isochrysis galbana. Negativeeffects of the filtrate on growth rates and motility of S. trochoideaand Tetraselmis sp. were recorded, suggesting that the toxinof the coccolithophore tested could be an exotoxin similar tothat produced by other non-calcifying members of the Prymnesiophyceae.The fact that certain coccolithophores were found to be toxicto invertebrates and were shown to exhibit allelopathic activitycould imply negative effects at different trophic levels incoastal areas.