Trace Metals in Mesozooplankton of the North Sea: Concentrations in Different Taxa and Preliminary Results on Bioaccumulation in Copepod Collectives (Calanus finmarchicus/C. helgolandicus)

Abstract

Trace metals (Cd, Cu, Zp, Pb, Ni) were determined in different zooplankton taxa to assess their role in the biogeochemical cycle in the North Sea. Results of semi-static bioaccumulation experiments on board ship using collectives of Calanus finmarchicus/C. helgolrindicris were in agreement with a net accumulation strategy, thus meeting an inevitable precondition for their utilization as biomonitors. Cd, Cu and Zn concentrations in field samples of zooplankton displayed a pronounced variability between taxa, with Cd ranging from 0.13 mg kg-1 (d.w.) in fish larvae to 5 I mg kg-1 in hyperiid amphipods. Almost no information is available about metal requirements of copepods. However, most of our and worldwide reported Cu concentrations in calanoid copepods (6-22 mg kg-1) coincided with estimates of enzymatic requirements of decapod crustaceans. Cd levels in Calurzrrs collectives increased significantly from 0.68 mg kg-1 in the German Bight to 11 mg kg-1 at some stations around Scotland above 59" N, in line with literature data reported for benthic decapod crustaceans. within the PRISMA multidisciplinary research project. The station grid is shown in Figure 1 (A, B). More information on the cruises is available in MEINCKE and BECKER (1993). HAARlCH et a[. (1993a) and PRISMA ( I 994).Samples for the taxonomic determination and quantification of zooplankton were taken with a vertically towed WP-2 net (mesh size 200 pm, from 3 rn above bottom to the surface), whereas samples for the determination of metals in zooplankton were obtained from a ring trawl (Californian Copepod Fishing Net, CALCOFI net, mesh size 300 pm), trawled with 2.5 knots from about 30 m depth to the surface. The CALCOFI net was equipped with a collecting jar made of polypropylene, fitted to the cod end of the net. Procedures for the biological assessment of the samples were followed as reviewed in KRAUSE and RADACH (1989) and FRANSZ et al. (1 99 I).On board ship, the zooplankton catches was transferred to polyethylene buckets and kept alive in aerated seawater at 12 "C, at least for 1-3 h. We assume completion of defaecation within this period, since gut transit times in these animals are less than 0.5 h (at 18 "C, REINFELDER and FISHER, 1991) and re-ingestion of food particles is most probably prevented by the turbulence of the water. Subsequently, the samples, still alive, were sorted under a binocular microscope, shortly rinsed with demineralized water and then stored frozen at -18 "C in acid cleaned Eppendorf reaction tubes ( I .5 mi, polypropylene). Whenever possible, samples were sorted to the species level. However, when preparing zooplankton samples for metal analyses (requiring several milligrams of dry weight, respectively), complicated procedures for biological assessment are not applicable, for instance, inspection of morphological structures of each specimen taken under a microscope. In such cases, only higher taxa were noted. A total of about 440 sorted samples (referred to as zooplankton collectives) were obtained from all cruises for ...

Heavy metals in zooplankton and decapod crustaceans from the Barents Sea

“…Possible explanations for these differences detected in field samples from the two studies may be related either to changing accumulation strategies of the copepods involved or to seasonally changing Cd absorption in copepods from food during summer when they intensively feed on phytoplankton, while the food uptake path is irrelevant in winter (see Ritterhoff and Zauke, 1997d for further discussion). Furthermore, local upwelling might be related to increased Cd bioavailabilities in seawater and hence increased uptake into copepods as hypothesised for the northern North Sea (Zauke et al, 1996a). Thus, we cannot regard our data for copepods as an indication of a Cd-anomaly without further evaluation.…”

“…To assure the quality of the sampling procedure, we followed the guidelines set up in Zauke et al (1996a) and Zauke and Petri (1993). The risk of contamination was largely reduced by, firstly, keeping the animals in sea water or on high-quality filter paper whenever possible.…”

“…Thus, in several studies macro-and meso-zooplankton organisms have been specifically used as biomonitors for assessment of the bioavailability of elements in marine systems, covering a variety of spatial and temporal scales (e.g. Ritterhoff and Zauke, 1997d;Zauke et al, 1996a). Their potential suitability is largely due to their worldwide presence, their major role in the food webs and their high contribution to the total biomass in marine systems.…”

“…An increasing body of information on metals in marine zooplankton has become available for specific regions such as the North Sea, the Greenland Sea and the Weddell Sea as intensively discussed in Zauke et al (1996a), Ritterhoff and Zauke (1997d) and . For other areas such as the Barents Sea recent information on metals in offshore zooplankton and crustaceans is largely lacking, in contrast to other components of the marine food web like inshore benthic invertebrates , fish (Zauke et al, 1999), sea birds and marine mammals (Booth and Zeller, 2005).The Barents Sea is an important area for commercial fisheries; with total annual yields reaching 3-4 million tons, it is comparable to Icelandic waters and the Norwegian Sea (Gjosaeter, 1995;Hansen et al, 1996).…”

Capacity of Salvinia minima Baker to Tolerate and Accumulate As and Pb

“…20 mg of freeze-dried plant material were digested with 200 lL HNO 3 (69 %) for 3 h at 80 C in a sand bath in tightly closed 2-mL Eppendorf reaction tubes [5]. The completely digested biomass was brought up to 2 mL with deionized water.…”