Journal Article

Phylogenetic composition and distribution of picoeukaryotes in the hypoxic northwestern coast of the Gulf of Mexico

Rocke, Emma, Jing, Hongmei, Liu, Hongbin

2013

Overview

Coastal marine hypoxic, or low‐oxygen, episodes are an increasing worldwide phenomenon, but its effect on the microbial community is virtually unknown by far. In this study, the community structure and phylogeny of picoeukaryotes in the Gulf of Mexico, which are exposed to severe hypoxia in these areas was explored through a clone library approach. Both oxic surface waters and suboxic bottom waters were collected in August 2010 from three representative stations on the inner Louisiana shelf near the Atchafalaya and Mississippi River plumes. The bottom waters of the two more western stations were much more hypoxic in comparison to those of the station closest to the Mississippi River plume, which were only moderately hypoxic. A phylogenetic analysis of a total 175 sequences, generated from six 18S rDNA clone libraries, demonstrated a clear dominance of parasitic dinoflagellates from Marine alveolate clades I and II in all hypoxic waters as well as in the surface layer at the more western station closest to the Atchafalaya River plume. Species diversity was significantly higher at the most hypoxic sites, and many novel species were present among the dinoflagellate and stramenopile clades. We concluded that hypoxia in the Gulf of Mexico causes a significant shift in picoeukaryote communities, and that hypoxia may cause a shift in microbial food webs from grazing to parasitism. The phylogenetic analysis of oxic surface and hypoxic bottom waters from the Gulf of Mexico during the summer of 2010 revealed a dominance of parasitic dinoflagellates and high picoeukaryote biodiversity in hypoxic samples. This study concluded that hypoxia in the Gulf of Mexico causes a significant shift in picoeukaryote community structure, including many novel species which could result in a significant shift in the microbial food web and biogeochemical cycle in marine coastal hypoxic waters.

• Publisher: Blackwell Publishing Ltd
• Subject: Alveolates / Biota / Dinoflagellates / Eukaryota - classification / Eukaryota - isolation & purification / Genetic Variation / Gulf of Mexico / hypoxia / MALV I and II / Molecular Sequence Data / Original Research / Oxygen - analysis / Phylogeny / picoeukaryotes / rDNA environmental sequences / RNA, Ribosomal, 18S - genetics / Seawater - chemistry / Seawater - parasitology / Sequence Analysis, DNA / Stramenopiles