Effects of microalgal exudates and intact cells on subtropical marine zooplankton

Abstract

Harmful algal blooms (HABs) affect coastal waters worldwide and very often lead to the disruption of seafood harvesting and commercial activities, because of potential hazards to human health associated with the consumption of contaminated mussels, crustaceans and fish. HAB events are frequently caused by outbreaks of toxin-producing dinoflagellates, which are subject to top-down control by zooplankton. The aim of this study was to analyze the effects of dinoflagellate exudates and intact cells on the survivorship and mobility of zooplankton taxa from a subtropical location (Ubatuba, Brazil). Lethal effects were observed in five out of six taxa investigated, three of which (copepod nauplii, tintinnids and gastropod larvae) when exposed to dinoflagellate exudates and two (rotifers and brachyuran zoeae) when exposed to intact cells. In addition, gastropod larvae displayed mobility impairment during exposure to dinoflagellate exudates. Only polychaete larvae were not apparently affected during the course of the experiments. Zooplankton responses usually varied according to the dinoflagellate species tested. For instance, exudates from Alexandrium tamiyavanichii, Gonyaulax sp. and Gymnodinium sp. decreased survivorship of planktonic copepod nauplii but did not affect bottom-dwelling harpacticoid nauplii, which were in turn killed by exudates from Prorocentrum lima, a epibenthic dinoflagellate. These results suggest that HAB events do not cause indiscriminate zooplankton mortality, but may instead generate community shifts and complex cascading effects through the pelagic and benthic food web. Speciesspecific monitoring of zooplankton responses to HABs is therefore an important step to understand the ecological implications of dinoflagellate outbreaks in coastal waters, and their impact on marine farming activities.

Analyzing the Impacts of Elevated-CO2 Levels on the Development of a Subtropical Zooplankton Community During Oligotrophic Conditions and Simulated Upwelling

“…Although Paracalanus sp. nauplii may exhibit adverse effects from feeding upon Alexandrium tamiyavanichii (Silva et al, 2013), we did not detect negative effects on nauplii abundances when relating them to the harmful algae abundance, but a delay in the reaction time likewise in aloricate ciliates, dinoflagellates and calanoid copepods. Accordingly, we based our conclusions for copepods on temporal trends and pCO 2 treatments rather than on possible effects of inedible/harmful food items.…”

Large-scale dinoflagellate bloom species Prorocentrum donghaiense and Karenia mikimotoi reduce the survival and reproduction of copepod Calanus sinicus

“…In other studies, Prorocentrum minimum and P. lima caused decreased naupliar survival and impaired developmental speeds (Galvão, 2004; Ismar et al ., 2008), although they also were shown to be a good food source to fuel reproduction in some copepod species (Turner et al , 2001; Carotenuto et al , 2002; Ianora et al , 2004a). Gymnodinium sanguineum and Karenia brevis also adversely affected naupliar survival (Murray & Marcus, 2002; Turner et al , 2012), and Silva et al (2013) reported that Alexandrium tamiyavanichii and Gonyaulax sp. caused 88–100% mortality of Acartia lilljeborgii nauplii within a short time.…”

Toxicity of benthic dinoflagellates on grazing, behavior and survival of the brine shrimp Artemia salina

“…Zooplankton species may be affected by toxins showing sub-lethal symptoms such as changes in pulsation frequency and immobility [24], grazing and motility suppression [25], and even lethal responses [26–27]. Moreover, HAB events may lead to shifts in community composition to more resistant species, generating complex cascading effects through the pelagic and benthic food webs [28]. Contaminated individuals may also transfer phycotoxins through the marine trophic web by the direct predation [29–30], by the elimination of toxic cells in biodeposits and feces and through the release of toxins after their death making toxins available for detritivorous species [31–33].…”