Impacts of climate change on harmful algal blooms (original) (raw)
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The exposure of marine mammals to the toxins associated with harmful algae can be lethal. Domoic acid (DA) is a biotoxin produced by the Pseudo-nitzschia group of diatoms many of which are now a common component of the Scottish phytoplankton community . DA is a potent excitatory neurotoxin that has caused large-scale mortality of marine mammals. We found harbour seals (Phoca vitulina) in Scotland are exposed to DA. Low levels, likely from recent exposure, were measured in the faeces and urine of live captured adult animals (using a direct competitive enzyme linked immunosorbent assay) and exposure was highest during August-September 2008 (7/32 of the faecal (22%) and 11/29 (38%) of the urine samples were positive). Median concentrations in positive faeces and urine were 25 ng/g and 6 ng/ml respectively. One positive pregnant female was subsequently found dead with 10 ng/ml DA in her amniotic fluid but the contribution of DA exposure to the cause of death could not be established. However, the highest levels in the study were found in anonymous faecal samples collected in September 2009 on the east coast of Scotland (up to 397 ng/g). Further studies are urgently needed to determine the importance of DA exposure to the population dynamics of Scottish harbour seals in light of the recently reported major population declines. ß
Over the past 15 years or so, several Scottish harbour seal (Phoca vitulina) populations have declined in abundance and several factors have been considered as possible causes, including toxins from harmful algae. Here we explore whether a link could be established between two groups of toxins, domoic acid (DA) and saxitoxins (STXs), and the decline in the harbour seal populations in Scotland. We document the first evidence that harbour seals are exposed to both DA and STXs from consuming contaminated fish. Both groups of toxins were found in urine and faeces sampled from live captured (n ¼ 162) and stranded animals (n ¼ 23) and in faecal samples collected from seal haul-out sites (n ¼ 214) between 2008 and 2013. The proportion of positive samples and the toxins levels measured in the excreta were significantly higher in areas where harbour seal abundance is in decline. There is also evidence that DA has immunomodulatory effects in harbour seals, including lymphocytopenia and monocytosis. Scottish harbour seals are exposed to DA and STXs through contaminated prey at potentially lethal levels and with this evidence we suggest that exposure to these toxins are likely to be important factors driving the harbour seal decline in some regions of Scotland.
Aquatic Mammals, 2010
Unusually high concentrations of the neurotoxin domoic acid (DA) were detected in a minke whale (Balaenoptera acutorostrata) carcass recovered during a severe harmful algal bloom (HAB), which occurred in southern California in April 2007. Cell fragments of the toxigenic diatom Pseudonitzschia australis were observed in whale gastric fluid and feces, corresponding to a dominance of Pseudo-nitzschia spp. in the phytoplankton community at the time of stranding. A high abundance of otoliths from a prominent DA vector, the northern anchovy (Engraulis mordax), were recovered in whale stomach contents, indicating trophic transfer of DA via the food web. Whale feces contained 258 µg DA per gram sample, exceeding DA concentrations reported for any marine mammal. DA intoxication was identified as the cause of mortality of this animal, expanding on the limited understanding of the impacts of DA-producing HABs on large whales.
Aquatic Mammals, 2010
Unusually high concentrations of the neurotoxin domoic acid (DA) were detected in a minke whale (Balaenoptera acutorostrata) carcass recovered during a severe harmful algal bloom (HAB), which occurred in southern California in April 2007. Cell fragments of the toxigenic diatom Pseudonitzschia australis were observed in whale gastric fluid and feces, corresponding to a dominance of Pseudo-nitzschia spp. in the phytoplankton community at the time of stranding. A high abundance of otoliths from a prominent DA vector, the northern anchovy (Engraulis mordax), were recovered in whale stomach contents, indicating trophic transfer of DA via the food web. Whale feces contained 258 µg DA per gram sample, exceeding DA concentrations reported for any marine mammal. DA intoxication was identified as the cause of mortality of this animal, expanding on the limited understanding of the impacts of DA-producing HABs on large whales.
Harmful Algal Blooms (HAB) are complex to manage due to their intermittent nature and their severe impact on the economy and human health. The conditions which promote HAB have not yet been fully explained, though climate change and anthropogenic intervention are pointed as significant factors. The rise of water temperature, the opening of new sea canals and the introduction of ship ballast waters all contribute to the dispersion and establishment of toxin-producing invasive species that promote the settling of emergent toxins in the food-chain. Tetrodotoxin, ciguatoxin, palytoxin and cyclic imines are commonly reported in warm waters but have also caused poisoning incidents in temperate zones. There is evidence that monitoring for these toxins exclusively in bivalves is simplistic and underestimates the risk to public health, since new vectors have been reported for these toxins and as well for regulated toxins such as PSTs and DSTs. In order to avoid public health impacts, there is a need for adequate monitoring programs, a need for establishing appropriate legislation, and a need for optimizing effective methods of analysis. In this review, we will compile evidence concerning emergent marine toxins and provide data that may indicate the need to restructure the current monitoring programs of HAB.
PLOS ONE, 2021
Despite a long-documented history of severe harmful algal blooms (HABs) in New England coastal waters, corresponding HAB-associated marine mammal mortality events in this region are far less frequent or severe relative to other regions where HABs are common. This long-term survey of the HAB toxins saxitoxin (STX) and domoic acid (DA) demonstrates significant and widespread exposure of these toxins in New England marine mammals, across multiple geographic, temporal and taxonomic groups. Overall, 19% of the 458 animals tested positive for one or more toxins, with 15% and 7% testing positive for STX and DA, respectively. 74% of the 23 different species analyzed demonstrated evidence of toxin exposure. STX was most prevalent in Maine coastal waters, most frequently detected in common dolphins (Delphinus delphis), and most often detected during July and October. DA was most prevalent in animals sampled in offshore locations and in bycaught animals, and most frequently detected in mystice...
Zenodo (CERN European Organization for Nuclear Research), 2022
Domoic acid, a marine neurotoxin causative of Amnesic Shellfish Poisoning (ASP) was first detected in Chilean shellfish in January 1997. The presence of domoic acid (DA) in shellfish extracts was determined by reverse-phase HPLC-UV. Domoic acid concentrations exceeded in some instances the maximum permitted level (MPL) of 20 mg kg-1 of tissue. The highest levels were found in mussels (Mytilus chilensis) and its presence was associated with diatom blooms of the genus Pseudo-nitzschia. Since the diatoms P. cf. australis and P. cf. pseudodelicatissima are frequent phytoplankton components with a wide distribution in Chilean coastal waters, a permanent ASP monitoring program was implemented by the National Fisheries Service (Sernapesca) in 2000. Analyses of live shellfish samples collected from production areas from Los Lagos Region (41 o 30' to 42 o 30' S) are reported from January 1999 to May 2021. A total of 94 from 57,882 samples (0.16%) were found to contain DA above 20 mg kg-1. Another 1,360 samples (2.35%) contained DA below MPL (0.01 to < 20 mg kg-1). Diatom blooms and domoic acid were detected every year. However, toxicity levels above MPL were observed only in nine of the 22 years of continuous monitoring. Regular increases in toxicity were observed mainly during the transition from spring to summer (October to March) with peaks during December and January. High detoxification rates of DA from mussels (T 1/2 < 4 ± 1 days) allowed the development of contingency plans during the blooms that minimized harvest closures. Despite its recurrent nature, the risk observed to date has been low, with no reported cases of poisoning in humans, marine mammals, or birds.
A B S T R A C T Current climate trends resulting in rapid declines in sea ice and increasing water temperatures are likely to expand the northern geographic range and duration of favorable conditions for harmful algal blooms (HABs), making algal toxins a growing concern in Alaskan marine food webs. Two of the most common HAB toxins along the west coast of North America are the neurotoxins domoic acid (DA) and saxitoxin (STX). Over the last 20 years, DA toxicosis has caused significant illness and mortality in marine mammals along the west coast of the USA, but has not been reported to impact marine mammals foraging in Alaskan waters. Saxitoxin, the most potent of the paralytic shellfish poisoning toxins, has been well-documented in shellfish in the Aleutians and Gulf of Alaska for decades and associated with human illnesses and deaths due to consumption of toxic clams. There is little information regarding exposure of Alaskan marine mammals. Here, the spatial patterns and prevalence of DA and STX exposure in Alaskan marine mammals are documented in order to assess health risks to northern populations including those species that are important to the nutritional, cultural, and economic well-being of Alaskan coastal communities. In this study, 905 marine mammals from 13 species were sampled including; humpback whales, bowhead whales, beluga whales, harbor porpoises, northern fur seals, Steller sea lions, harbor seals, ringed seals, bearded seals, spotted seals, ribbon seals, Pacific walruses, and northern sea otters. Domoic acid was detected in all 13 species examined and had the greatest prevalence in bowhead whales (68%) and harbor seals (67%). Saxitoxin was detected in 10 of the 13 species, with the highest prevalence in humpback whales (50%) and bowhead whales (32%). Pacific walruses contained the highest concentrations of both STX and DA, with DA concentrations similar to those detected in California sea lions exhibiting clinical signs of DA toxicosis (seizures) off the coast of Central California, USA. Forty-six individual marine mammals contained detectable concentrations of both toxins emphasizing the potential for combined exposure risks. Additionally, fetuses from a beluga whale, a harbor porpoise and a Steller sea lion contained detectable concentrations of DA documenting maternal toxin transfer in these species. These results provide evidence that HAB toxins are present throughout Alaska waters at levels high enough to be detected in marine mammals and have the potential to impact marine mammal health in the Arctic marine environment.