Effects of depth, habitat, and water motion on the abundance and distribution of ciguatera dinoflagellates at Johnston Atoll, Pacific Ocean

Abstract

A major impediment to understanding the seemingly random occurrence of ciguatera toxicity is uncertainty regarding the field ecology of benthic dinoflagellates that introduce toxins into the coral reef food web. Although broad generalizations have been made, past studies have often yielded contradictory results, particularly between ecological patterns documented in the Pacific versus the Caribbean. This study employed standardized methodology to investigate the distribution and abundance of toxigenic benthic dinoflagellates from the genera Gambierdiscus, Prorocentrum, Ostreopsis, and Amphidinium at Johnston Atoll, Pacific Ocean, to determine how water motion, depth and habitat type influence patterns of biodiversity. Sampling stations located in lagoon and channel habitats in the atoll supported the highest total dinoflagellate abundance, while dinoflagellate numbers were lower at sampling stations in back reef and reef crest habitats. Total dinoflagellate abundance was primarily determined by the degree of water motion; however, this effect varied among genera. Of the 4 genera surveyed, 3 (Gambierdiscus, Prorocentrum, Amphidinium) were negatively correlated with water motion; conversely, Ostreopsis had a positive correlation. Habitat separation was observed between Ostreopsis and Prorocentrum spp., which were negatively correlated. Gambierdiscus was present at all sampling stations and at all habitats, even though it was rarely the dominant genus. This study provides a characterization of the ciguatera dinoflagellate community across a variety of coral reef habitats, contributing to an accurate and coherent characterization of the population dynamics of this important dinoflagellate community.KEY WORDS: Ciguatera fish poisoning · Gambierdiscus · Prorocentrum · Ostreopsis · Johnston Atoll · Epiphytic · Coral reefs Resale or republication not permitted without written consent of the publisher

Cambios estacionales en conjuntos de dinoflagelados epifíticos cerca de la costa norte de la Península de Yucatán, Golfo de México

“…in the two study areas was very heterogeneous; the same was observed at Johnston Atoll, where Gambierdiscus spp. reached 4.00x10 2 cells g -1 WW (Richlen & Lobel, 2011). The maximum population densities observed in Yucatan waters were comparable to maxima reported for Gambierdiscus spp.…”

“…At Johnston Atoll in the Pacific Ocean, the abundance of Gambierdiscus spp. was negatively correlated with water motion (Richlen & Lobel, 2011 (20.5-22.7 o C). Curiously, the absence of Gambierdiscus spp.…”

“…This fact may be explained by the preference of Ostreopsis species for a particular substrate. Furthermore, it was shown that Ostreopsis species in general are characteristic of high energy reef sites, being positively correlated with water motion (Richlen & Lobel, 2011).…”

“…The major exception is studies that have followed the seasonality of individual species that were thought to cause ciguatera (Bagnis et al, 1985;Carlton & Tindall, 1985;Gillespie et al, 1985;Mitchell, 1985;Ballantine et al, 1988;Bomber et al, 1988;Tindall & Morton, 1998;Chinain et al, 1999;Vila et al, 2001;Levasseur et al, 2003). Habitat preference, the influence of environmental factors and population dynamics of the epiphytic dinoflagellates are still poorly known (Richlen & Lobel, 2011). In the southern Gulf of Mexico, the only study on seasonality (covering eight months) of epiphytic dinoflagellates was conducted in the state of Veracruz by Okolodkov et al (2007).…”

Variability patterns of epibenthic microalgae in eastern Tunisian coasts

“…The high concentrations of P. lima on Posidonia raise the problem of its sampling representativeness, since most monitoring programmes focused on the water column, which might lead to an underestimation of the species abundance (Marr et al 1992). P. lima concentrations showed a significant relationship between P. oceanica and the water column (R 2 =0.79), suggesting that the species, being a weekly swimming dinoflagellate that can even be affected by low water motion conditions (Richlen and Lobel 2011), might move from one compartment to another. The establishment of a direct relationship between the concentration of this species in the water column and on macrophytes allows us to assess the concentration in one compartment by referring to the concentration in the other one.…”