Southern right whale (Eubalaena australis) calf mortality at Península Valdés, Argentina: Are harmful algal blooms to blame?

Abstract

Península Valdés (PV) in Argentina is an important calving ground for southern right whales (SRWs, Eubalaena australis). Since 2005, right whale mortality has increased at PV, with most of the deaths (~90%) being calves <3 mo old. We investigated the potential involvement of harmful algal blooms (HABs) in these deaths by examining data that include: timing of the SRW deaths, biotoxins in samples from dead SRWs, abundances of the diatom, Pseudo‐nitzschia spp., and the dinoflagellate, Alexandrium tamarense, shellfish harvesting closure dates, seasonal availability of whale prey at PV and satellite chlorophyll data. Evidence of the whales' exposure to HAB toxins includes trace levels of paralytic shellfish toxins (PSTs) and domoic acid (DA) in tissues of some dead whales, and fragments of Pseudo‐nitzschia spp. frustules in whale feces. Additionally, whales are present at PV during both closures of the shellfish industry (due to high levels of PSTs) and periods with high levels of Pseudo‐nitzschia spp. and A. tamarense. There is a positive statistical relationship between monthly Pseudo‐nitzschia densities (but not A. tamarense) and calf deaths in both gulfs of PV.

Species occurrence of the potentially toxigenic diatom genus Pseudo-nitzschia and the associated neurotoxin domoic acid in the Argentine Sea

“…Similarly, DA has been frequently detected in phytoplankton samples from different zones of the Argentine Sea in the last few years (Negri et al, 2004;Sastre et al, 2007;Cadaillón, 2012;Krock et al, 2015). Indeed, Pseudo-nitzschia blooms have been suggested as potentially responsible for calf mortalities of southern right whales along the Valdés Península Wilson et al, 2015). During these episodes, DA production was mainly associated with elevated cell densities of P. australis (Negri et al, 2004) or P. fraudulenta (Cleve) Hasle (Sastre et al, 2007), but the co-occurrence of several other Pseudonitzschia species (Cadaillón, 2012;Krock et al, 2015), makes it difficult to unequivocally identify the responsible taxa.…”

Post-mortem findings in southern right whales Eubalaena australis at Península Valdés, Argentina, 2003-2012

“…Península Valdés is a significant source of bivalve mollusks for human consumption in Argentina, and algal toxins and harmful algal blooms (HABs) have been monitored in PV since 1985 (Wilson et al 2015). In general, elevated HAB species and associated biotoxins such as saxitoxin and domoic acid have not been linked to significant human or animal morbidity or mortality at PV, though biotoxin-or HAB-related human and seabird deaths have periodically occurred (Wilson et al 2015).…”

“…In general, elevated HAB species and associated biotoxins such as saxitoxin and domoic acid have not been linked to significant human or animal morbidity or mortality at PV, though biotoxin-or HAB-related human and seabird deaths have periodically occurred (Wilson et al 2015). In 2 previous studies, low levels of saxitoxin or domoic acid were detected in tissues from dead whales (Wilson et al 2015), and frustules of potentially toxic Pseudo-nitzschia were identified in feces of living and dead PV SRWs (D'Agostino et al 2015). However, spatial or temporal relationships between algal biotoxin production and whale mortality peaks were not found.…”

“…Many aspects of SRW ecology, including population dynamics, behavior, sound production/vocalization, and aspects of reproduction, calving, and calf rearing, have been continuously or periodically studied at PV since the early 1970s (Cummings et al 1972, Payne et al 1983, Thomas & Taber 1984, Payne 1986, Best & Ruther 1992, Best & Schell 1996, Rowntree et al 1998, Cooke et al 2001, Leaper et al 2006). More recently, with the establishment in 2003 of the Southern Right Whale Health Monitoring Program (SRWHMP), investigations to understand SRW health and causes of mortality have also been pursued (Uhart et al 2008, La Sala et al 2012, Martino et al 2012, Rosas et al 2012, Rowntree et al 2013, Sironi et al 2014, Marón et al 2015, Torres et al 2015, Wilson et al 2015.…”

Lessons Learned from the NOAA CoastWatch Ocean Satellite Course Developed for Integrating Oceanographic Satellite Data into Operational Use

“…Runchie and Muhling (both class of 2017) used satellite data to describe the habitat preferences of bluefin tuna in the California Current [32]. Post-course collaboration between course instructors and participants has resulted in the development of habitat models [33,34], and the use of satellite chlorophyll measurements to assess the potential influence of harmful algal blooms on the decade-long increase in Southern Right Whale mortality [35].…”