Effect of high temperature on the meiofauna composition, abundance, and biomass in a zone of geophysical anomalies

Abstract

Meiofauna are an excellent assemblage for studying how environmental changes affect numerous invertebrates. Meiofaunal distribution can be influenced by several key environmental factors which may differ among habitats and could be too numerous to evaluate. The Wagner and Consag shallow basins are located at the northern end of the Gulf of California. These basins are a young rift system where intense gas discharge has been reported and correlated to anomalously high heat flow (105 W/m2) and temperature (50.2°C in this study). The aim of this study is to evaluate the effects of environmental conditions on the abundance and biomass distribution of the meiofauna in these two shallow and geologically anomalous basins and to determine which of the measured variables are key factors. Sediment samples were collected during the “Sísmica 2015” expedition aboard R/V “Alpha Helix” during September 2015, within a depth range of 39–237 m. A total of 609 organisms were separated and six taxonomic groups were identified: Gastropoda, Polychaeta, Nematoda, Kinorhyncha, Ostracoda, and Harpacticoida. Meiofauna abundance ranged from 0 to 114.11 ind/10 cm2 and biomass ranged from 0 to 300.02 μg Corg/10 cm2. Though abundance and biomass were found to be correlated to sediment temperature, the main factor associated with the observed meiofaunal distribution was grain size temperature, however, was confirmed as the most important environmental factor as it was responsible for the greatest spatial variation in meiofaunal composition throughout the Wagner and Consag basins, where high temperature stations showed lower abundances. There is still very little known about meiofauna from extreme environments and their clear responses to these extreme conditions is lacking in the published literature. There is an urgent need to understand the biology and ecology of the meiofauna taxa that thrive in these natural environments. The findings in this study may provide some insights into these ecological processes, but more importantly they may be of use in assessing the vulnerability of benthic communities to future anthropogenic disturbances.