Phycotoxin accumulation in zooplankton feeding on Alexandrium fundyense--vector or sink?

Abstract

Paralytic shellfish poisoning (PSP) toxins are produced by dinoflagellates of the genus Alexandrium, which form blooms in the Gulf of Maine (Anderson et al., 1994). It is well known that suspension-feeding shellfish can consume toxic cells of Alexandrium spp. and accumulate PSP toxins, and that such contaminated shellfish are a threat to public health and result in economic loss to the fishing and aquaculture industries (Shumway et al., 1988). Zooplankton are also major consumers of phytoplankton, including Alexandrium spp.; the presence of PSP toxins in wild zooplankton populations of the Gulf of Maine has been documented in several studies (White, 1979, 1980, 1984). These studies have shown that mesozooplankton can attain body burdens of these toxins that are inimical or even fatal to vertebrate zooplanktivores such as clupeid fishes and whales. Larval fish are even more susceptible to adverse effects from consumption of zooplankton contaminated by PSP toxins (White et al., 1989; Robineau et al., 1991a,b). Nevertheless, research suggests that only a fraction of the total toxin from Alexandrium spp. cells acquired during feeding activity is retained in the tissues of zooplankton grazers. White conducted toxin accumulation studies with adult copepods, Acartia clausi (= A. hudsonica), and barnacle nauplii, Balanus sp. (= Semibalanus sp.) at high densities (10-13 individuals ml-1), fed Alexandrium fundyense (= Gonyaulax excavata) at ~ 3 ϫ 10 3 cells ml-1 (White, 1981). At such high densities of zooplankton and toxic cells, both grazer species accumulated high toxin levels [19-54 µg saxitoxin equivalents (µgSTXeq) g-1 wet weight] within 6 h. Toxin retained in copepod tissues, expressed as a percentage of total toxin ingested, ranged from ~10% for A. clausi to ~32% for Balanus sp. White used a modification of the Association

Paralytic shellfish poisoning (PSP) toxins in North Atlantic right whales Eubalaena glacialis and their zooplankton prey in the Bay of Fundy, Canada

“…Investigations of PSP toxin accumulation have been conducted for other copepods (e.g. Eurytemora herdmani, Acartia tonsa), showing that grazer toxin profiles are highly species-specific, ranging from quite similar to very different compared to those of their algal prey (Teegarden & Cembella 1996, Teegarden et al 2003. Similar results have been documented for filterfeeding bivalves (Bricelj & Shumway 1998).…”

Comparison of the functional and numerical responses of resistant versus non-resistant populations of the copepod Acartia hudsonica fed the toxic dinoflagellate Alexandrium tamarense

“…Copepods have been are known to accumulate toxins in relation to how much they ingest regardless of whether the algae were provided as a monoculture or as part of a mixed diet (Teegardern and Cembella, 1996;Teegarden et al, 2003). Our result demonstrate that for A. tamarense, copepod ingestion rate is strongly dependent on algal concentration for both resistant and non-resistant populations, but that the slopes of the functional response curves are dependent upon population biogeography and resistance (Table 1).…”

Intoxicated copepods: ingesting toxic phytoplankton leads to risky behaviour

“…Copepods are important grazers of HABs as they can serve as vectors for toxin entry into pelagic food webs [6,7]. Therefore, much work has been done to determine the effects of harmful algae on copepod survival and fitness.…”