Chronic contamination in the southern Gulf of Mexico coastal zone, as evidenced by meiofauna biological traits

Abstract

Meiofauna is a good pollution indicator that reflects the ecological status of sediments and their linkages with overlying communities. However, long-term monitoring of this fauna is a developing research activity in most marine ecosystems. This study assessed seasonal spatial and temporal changes in meiofauna composition, abundance, and biological traits in the southern Gulf of Mexico sublittoral zone. We examined two questions: How do the meiofauna attributes vary spatially and seasonally? Which contaminants correlate with the distribution of meiofauna biological traits? We analysed sediment characteristics, metals, hydrocarbons, and meiofauna data collected at shallow coastal sites (<10 m) during eight annual surveys (2005–2020). Organic contamination increased when natural disturbances occurred, mainly in the dry season, decreasing the number of nematode taxa and increasing their abundance. During the eight yearly sampling events, nematodes, harpacticoid copepods, and polychaetes varied according to the sedimentary gradient. Chronic contamination (aromatic compounds, Cr, V, Cd, Cr) covaried with meiofauna biological traits. Our results point out meiofauna taxa (e.g., Anoplostoma, Halalaimus, Monhystera, harpacticoid copepods, saccocirrid polychaetes) as bioindicators of resilient and disturbed sites for terrigenous and transitional sediments, while in carbonate sediments dominated sensitive species. Resilient sites were exposed to the Grijalva-Usumacinta river discharges and the oil industry. Tolerant and opportunistic taxa such as the nematodes Anoplostoma and Xyala were classified as colonisers and non-selective deposit feeders. Conversely, sensitive taxa such as Halalaimus and harpacticoid copepods were semelparous, carnivorous, and persisters.