Artspezifische Merkmale der Faeces von vier dominierenden Copepodenarten der Kieler Bucht

Zusammenfassung 1. Die Kotballen der planktischen CopepodenartenAcartia bifilosa, Centropages hamatus, Oithona similis undPseudocalanus elongatus werden in ihrer Form, Länge und Breite beschrieben.2. Die aus Länge, Breite und Grundform der Faeces berechneten durchschnittlichen Volumina liegen zwischen 13 × 10³ µm³ für beide Geschlechter der ArtOithona similis und 348 × 10³ µm³ für die Kotballen der Weibchen der ArtAcartia bifilosa.3. Die Dimensionen der Faeces der vier untersuchten Arten zeigen in mindestens einem der untersuchten Parameter signifikante Unterschiede. Im Falle der ArtenAcartia bifilosa undCentropages hamatus sind auch die Größen der Kotballen beider Geschlechter signifikant verschieden.4. Ein Vergleich von Labor- und Freilanduntersuchungen zeigt, daß die in sedimentiertem Seston gefundenen Faeces planktischer Copepoden sich mit Hilfe der experimentell gefundenen Charakteristika den dominierenden Arten zuordnen lassen.

---

Species-characteristics of the fecal pellets of four dominating copepod species of Kiel bight

Mean length, width and shape of the fecal pellets of the four planktonic copepod species,Acartia bifilosa, Centropages hamatus, Oithona similis andPseudocalanus elongatus, were studied. Mean volumes of the fecal pellets of the different species vary between 13 × 10³ µm³ (males and females ofOithona similis) and 348 × 10³ µm³ (females ofAcartia bifilosa). The dimensions of the fecal pellets of the four species examined reveal significant differences in at least one of the criteria studied. InAcartia bifilosa andCentropages hamatus even the length and width of the fecal pellets of the two sexes are different. With respect to the characteristics described, a comparison made between fecal pellets found in cultures with those obtained from sediment of the Baltic Sea (Kiel Bight) has shown that the latter may be attributed to the copepod species under consideration.

     

Feeding rates and productivity of the copepod Acartia bifilosa in a highly turbid estuary; the Gironde (SW France)

Acartia spp. are the dominant copepod species in the Gironde estuary, seaward of the turbidity maximum area. Acartia bifilosa develop a large population in spring and early summer whereas Acartia tonsa appear in late summer. High values and high variability of chlorophyll a/suspended particulate matter ratio are found seaward of the turbidity maximum area. Feeding rates of A. bifilosa were measured by fluorometry. Phytoplankton ingestion was found to be highly variable, between 8 to 80% of copepod carbon body weight. Except for adult females, copepods were heavier in summer than in winter. PB ratios, estimated by the instantaneous growth rate method, varied from 0.03 d^–1 to 0.14 d^–1. The gut contents and P/B ratios of Acartia bifilosa were related to chl a/SPM ratio. From those data, and a few obtained for A. tonsa, it is concluded that only in summer months phytoplankton ingestion is enough to maintain secondary production.     

The longevity of three generations of normal and pollution-impacted Acartia clausi (Copepoda) populations in the Saronicos Gulf (Greece)

The longevity of two populations of the planktonic copepod Acartia clausi in the Saronicos Gulf was estimated. One group lived in a heavily polluted area, the other group in a relatively clean area. Three annual generations were studied. A comparison was also made between fed and unfed animals. A temperature of 14°C appeared to be the most favourable for the survival of Acartia; however, the optimum survival temperature depended also upon the generation to which the Acartia belonged. The acclimatization temperature has a strong influence on survival. Acartia in its natural environment thrives best and has maximum longevity at colder temperatures. The pollution-adapted Acartia population survived longer under laboratory-controlled conditions than the population living in a non-polluted area.     

Seasonal dynamics of Acartia bifilosa and Eurytemora affinis (Copepods: Calanoida) in relation to abiotic factors in the northern Baltic Sea

Distributions in the time and space

Seasonal dynamics of Acartia bifilosa and Eurytemora affinis (Copepods: Calanoida) in relation to abiotic factors in the northern Baltic Sea     

Induction of toxin production in dinoflagellates: the grazer makes a difference

The dinoflagellate Alexandrium minutum has previously been shown to produce paralytic shellfish toxins (PST) in response to waterborne cues from the copepod Acartia tonsa. In order to investigate if grazer-induced toxin production is a general or grazer-specific response of A. minutum to calanoid copepods, we exposed two strains of A. minutum to waterborne cues from three other species of calanoid copepods, Acartia clausi, Centropages typicus and Pseudocalanus sp. Both A. minutum strains responded to waterborne cues from Centropages and Acartia with significantly increased cell-specific toxicity. Waterborne cues from Centropages caused the strongest response in the A. minutum cells, with 5 to >20 times higher toxin concentrations compared to controls. In contrast, neither of the A. minutum strains responded with significantly increased toxicity to waterborne cues from Pseudocalanus. The absolute increase in PST content was proportional to the intrinsic toxicity of the different A. minutum strains that were used. The results show that grazer-induced PST production is a grazer-specific response in A. minutum, and its potential ecological importance will thus depend on the composition of the zooplankton community, as well as the intrinsic toxin-producing properties of the A. minutum population.     

Acartia tonsa: a species new for the Black Sea fauna

The presence of Acartia tonsa in Black Sea waters (South Crimean coast, Ukraine) is reported for the first time. A. tonsa may be a recently introduced species in the Black Sea. Morphological features of the adults have been shown by S.E.M.     

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.     

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.     

Copepod biomass in an estuarine and a stagnant brackish environment of the S. W. Netherlands

In the mesohaline zone of the Westerschelde estuaryEurytemora affinis is the dominant copepod, demonstrating large biomass values nearly throughout the year. In the meso-polyhaline Lake VeereAcartia tonsa is abundant, mainly during summer. In spring a small population ofEurytemora americana is found. The tidal estuary harboured far denser copepod populations throughout the year than the stagnant brackish lake water. The average yearly copepodid+adult biomass in the Westerschelde estuary was approx. 850 mg/m³ (wet weight), in Lake Veere approx. 130 mg/m³. Temporarily low oxygen values did not influence negatively the copepod populations in the Westerschelde estuary. The seasonal distribution of the dominant copepods in both areas is explained in the light of recent litterature data. PerennialEurytemora affinis abundance in the Westerschelde estuary must be mainly caused by large concentrations of nannodetritus particles, bacteria included, throughout the year.Acartia tonsa in Lake Veere has to thrive mainly on nannophytoplankton. Communication no. 141 of the Delta Institute for Hydrobiological Research, Yerseke, The Netherland.     

Beiträge zum Mesozooplankton des Nordsylter Wattenmeers

Contributions to the mesozooplankton of the northern Wadden Sea of Sylt. From June 1975 to June 1976 temperature, salinity, mesozooplankton (>76 µm), phytoplankton and seston (dry weight, particulate organic carbon and nitrogen) were measured at different stations in the northern Wadden Sea of Sylt (German Bight, North Sea). Maxima of the planktonic copepods, which form the biggest part of the zooplankton, occurred in the summer months from June to September. Larval development from nauplii to adults was observed inAcartia clausi, Acartia discaudata, Centropages hamatus andTemora longicornis; generation times ranged from 3 (Temora longicornis) to 7 1/2 weeks (Centropages hamatus) at ca. 20 °C. Organic carbon produced by zooplankton was about 0.4 g C m^–3 year^–1 and zooplanktonic carbon decomposed in the area studied amounted to about 1.4 g C m^–3 year^–1. Meroplanktonic larvae made up ca. 60 % of the organic carbon produced by zooplankton, indicating great influence of the benthos on the water column in this very shallow part of the German Bight.     

钦州湾秋季和春季浮游动物分布特征及影响因素

为了解钦州湾浮游动物群落的时空分布特征及与主要环境因子的关系,于2014年10月和2015年3月进行了秋季和春季两航次的调查。结果表明:该海湾的浮游动物群落有明显的季节变化。秋季共鉴定出12类87种,其中优势种有太平洋纺锤水蚤(Acartia pacifica)、肥胖三角溞(Evadne tergestina)、亨生莹虾(Lucifer hanseni)、百陶箭虫(Sagitta bedoti)和长尾类幼虫(Macrura larvae);春季共鉴定出11类48种,优势种为中华哲水蚤(Calanus sinicus)和太平洋纺锤水蚤;秋季浮游动物的平均丰度、生物量和多样性指数(528.92个/m~3、110.60 mg/m~3和2.22)均高于春季(48.30个/m~3、61.10 mg/m~3和1.70)。空间分布上,钦州湾外湾浮游动物丰度、生物量和多样性指数的平均值皆高于内湾。多维尺度分析表明,秋季内湾群落相似性较高,春季外湾浮游动物群落相似性较高。相关性分析表明盐度与营养盐是影响钦州湾浮游动物分布的主要环境因子。与2011—2012年数据相比,钦州湾浮游动物群落结构已趋于单一化和小型化,以致生物量明显下降。这一现象主要与钦州湾海水富营养化以及大面积高密度牡蛎养殖有密切的关系。     

Copepods grazing on <Emphasis Type="Italic">Coscinodiscus wailesii</Emphasis>: a question of size?

Grazing of female copepods, Acartia clausi and Temora longicornis, on the large centric diatom Coscinodiscus wailesii, was studied in the laboratory. While A. clausi females did not feed on C. wailesii, T. longicornis showed a skilful handling of these large algae. The cells were not completely ingested but copepods bit a small piece out of the silica wall and then ingested the cell content only. Faecal pellet analyses showed little remains of the silica walls, and most of the content could only be classified as undefined matter. Therefore the general analyses of faecal pellets and gut content of copepods from the field must be interpreted with caution.     

Detritivores feeding on poor quality food are more sensitive to increased temperatures

Copepods of the genus Acartia dominate zooplankton assemblages in northwestern Atlantic estuaries, many of which originated after the last glacial maximum 10,000–18,000 years ago. Acartia hudsonica occurs, at least seasonally, in estuaries from Chesapeake Bay to Labrador/Newfoundland. We sequenced the mitochondrial gene Cytochrome B (CytB) of 75 individuals of A. hudsonica from 26 estuaries from New Jersey to Maine, covering four biogeographic regions, and 11 individuals of Acartia tonsa from four of these estuaries in the southern part of the sampling range. A. hudsonica exhibited exceptionally high intraspecific DNA sequence variation. Uncorrected p-distances between sequences ranged from 0.3 to 31%. Five highly divergent sequence groups differed in frequencies across populations and biogeographic regions. One sequence group dominated northern localities, and two sequence groups were found at intermediate to high frequencies in two southern biogeographic regions. Ages of the sequence groups were estimated to be 11, 13, 30, and 37 million years, by applying a molecular clock calibrated by divergence in Alpheus snapping shrimps across the Isthmus of Panama. These ages were compared with independent biogeographic paleoceanographic data, and may have coincided with periods of global climate change over the past 40 MY.     

Pollution effects on the phytoplankton-zooplankton relationships in an inshore environment

The quantitative and qualitative relationships between the phytoplankton and zooplankton populations were examined for one year in an inshore environment (Elefsis Bay) of the Aegean Sea. It was found that quantitative relationships among these populations were influenced by the trophic level of the environment and their stocks were significantly correlated only in non-polluted conditions. The quantitative relationship between the principal grazers in the zooplankton population (Acartia clausi, Oithona nana) and the phytoplankton dominant species Exuviaella baltica, upon which these copepods were believed to graze preferentially, was tested and the results were discussed.     

Seasonal variations in copepod body length: a comparison between different species in the Lagoon of Venice

The seasonal variation in length of the most abundant copepod species in the lagoon of Venice were compared and the relative influence of temperature, chlorophyll concentration and salinity examined. Temperature seems to be the primary factor influencing copepod body length in the lagoon of Venice, but the different species vary markedly in their response. Calanoid copepods (Acartia clausi, A. tonsa, Paracalanus parvus and Centropages ponticus) showed a more definite trend of size variation with temperature than the cyclopoids (Oithona nana and O. similis) and the harpacticoid Euterpina acutifrons. The size of the poecilostomatoids Oncaea media and O. subtilis was not affected by temperature, and was almost constant over time. Differences in the metabolic rates, longevity and specialization of calanoid, cyclopoid and harpacticoid copepods could explain their different responses to temperature.     

Factors affecting feeding selectivity of visual predators on the copepod Acartia tonsa: locomotion,visibility and escape responses

Visual predation by fish on copepods involves prey encounter, attack and capture; during any of these processes prey selection can occur. Developmental changes in copepods, including increases in swimming speed, size and image contrast increase the encounter rate and distance at which they can be detected by predators. Copepods compensate for this increase vulnerability with age through diel vertical migration and improved escape capabilities. This study quantifies the changes in swimming speed and movement pattern with developmental stage of the copepod Acartia tonsa, using a video-computer system for motion analysis. Changes in visible size and image contrast with developmental stage were quantified under simulated natural illumination conditions using a video based image analysis system. The escape responses of the naupliar stages of the copepod Acartia tonsa were quantified in response to a stationary pipette sucking in water at a constant speed. Accurate quantification of the parameters that affect feeding selectivity of planktivorous fish will provide the basis for evaluation of their relative importance in future studies.     

Comparative spring distribution of zooplankton in three macrotidal European estuaries

The zooplankton of three european estuaries (Ems, Gironde and Westerschelde) was investigated during spring 1992 by means of samples taken along the salinity gradient. The three estuaries are comparable in terms of total area, flushing time and salinity gradient but differ by their level of eutrophication (highest in the Westerschelde), suspended matter concentration (highest in the Gironde) and potential phytoplankton production (highest in the Ems). Copepods and meroplankton dominated the zooplankton in the three estuaries. The dominant copepod species were Eurytemora affinis and Acartia bifilosa. The distribution of E. affinis along the salinity gradient differed between the estuaries. Peaks of abundance were observed at 0 PSU in the Gironde, 6 PSU in the Ems and 9 PSU in the Westerschelde. The downstream shift of the population in the Westerschelde was likely due to anoxic conditions occurring in the oligohaline zone. In the Gironde the downstream distribution of E. affinis was limited by the very high suspended matter concentration found in the maximum turbidity zone. Whatever the estuary, the parameters of the population of E. affinis and maximum abundance values were similar. However, the influence of the better quality of the available food was suggested in the Ems where individual dry weights and egg production were higher than in the two other estuaries. The influence of a good quality of food in the Ems was confirmed by the development of a large population of Acartia bifilosa (as abundant as E. affinis) and highest values of adult individual weights.The meroplankton (essentially Polychaete and cirripede larvae) was much more developed in the Ems than in the Westerschelde and Gironde. This was likely due to the large extent of mudflats and hard substrates in the Ems favouring adult settlement and hence the number of larvae locally produced.     

Copepod community structure and abundance in a tropical mangrove estuary,with comparisons to coastal waters

Zooplankton, sampled at five stations from the upper Sangga estuary (7 km upstream) in Matang Mangrove Forest Reserve (MMFR), Malaysia, to 16 km offshore, comprised more than 47% copepod. Copepod abundance was highest at nearshore waters (20,311 ind m⁻³), but decreased toward both upstream (15,572 ind m⁻³) and offshore waters (12,330 ind m⁻³). Copepod abundance was also higher during the wetter NE monsoon period as compared to the drier SW monsoon period, but vice versa for copepod species diversity. Redundancy analysis (RDA) shows that copepod community structure in the upper estuary, nearshore and offshore waters differed, being influenced by spatial and seasonal variations in environmental conditions. The copepods could generally be grouped into estuarine species (dominantly Acartia spinicauda Mori, Acartia sp1, Oithona aruensis Früchtl, and Oithona dissimilis Lindberg), stenohaline species (Acartia erythraea Giesbrecht, Acrocalanus gibber Giesbrecht, Paracalanus aculateus Giesbrecht, and Corycaeus andrewsi Farran) and euryhaline species (Parvocalanus crassirostris Dahl, Oithona simplex Farran, and Bestiolina similis (Sewell)). Shifts in copepod community structure due to monsoonal effects on water parameters occurred at the lower estuary. Copepod peak abundance in mangrove waters could be associated with the peak chlorophyll a concentration prior to it. Evidence of copepod consumption by many species of young fish and shrimp larvae in the MMFR estuary implies the considerable impact of phytoplankton and microphytobenthos on mangrove trophodynamics.     

Zooplankton variability related to environmental changes in a eutrophic coastal lagoon in the Po Delta

Zooplankton variability in a lagoon of the Po Delta, the Sacca di Goro, was studied in relation to changes in its hydrodynamic and hydrological features. From 1987 to 1992 the lagoon was affected each summer by severe anoxia due to the decomposition of dense and widespread beds of Ulva rigida. In August 1992 a canal was opened through the sand bank closing off the lagoon from the sea in order to improve the water circulation. This hydraulic intervention led to significant environmental changes in the lagoon: during the two subsequent years the summer dystrophic crises were brief and less severe, due to a sharp decrease in the Ulva cover. At the same time a clear increase in phytoplankton biomass values was observed. Following the opening of the channel, the most remarkable change in zooplankton was a significant density increase of calanoids, particularly of Acartia tonsa.