Chapter 7 - Biodiversity of deep ocean on development of biofilms: Biofouling communities and corrosion performance of materials

Abstract

Biofilms are ubiquitous and the predominant mode of living in microorganisms. Biofilms exist as surface-attached communities to hard substrata, minerals, and sand particles. Samples of ocean floor crusts and rocks have shown the microbial diversity of deep oceans. They have been found to be different from planktonic forms at the same location. Studies pertaining to macrofouling in the deep sea environment at depths in excess of 1000 m is scarce. However, water depths upto 5000 m have been reported with many species from various invertebrate phyla. Global oceans can be classified into three major extreme environmental systems based on their location and biogeochemistry, which drives microbial diversity. The most studied among them is hydrothermal vent ecosystems, which disperse geothermal fluids with temperatures ranging from 27°C (shallow) to 400°C (deep ocean). Vent ecosystems have distinct microbial consortia compared with oligotrophic oceanic waters, which differ in temperature within a distance of a few meters. The second most investigated systems are cold seeps, which are rich in sulfates. The microbial consortia of this system are shaped by sulfate oxidizers and reducers. Compared with the earlier two environments, seamount ecosystems are more productive and highly diverse, ranging from corals to fish and invertebrates. The planktonic flora and fauna of seamount ecosystems are characterized, compared with the benthic biota, because there is a lack of instrumentation to sample those at greater depths. In general, there is a similarity in the microbial consortia of deep seawater and that of extreme environments with surface seawater. However, deep-sea microbial consortia have developed mechanisms to withstand high-pressure low/high temperatures and energy requirements such as chemo auto/lithotrophic modes. The similarity in the microbial genera between surface and deep water may be attributed to the sinking of organic detrital matter into the deep sea and upwelling of deep ocean water. These may have mixed the microbial consortia. Adaptation and acclimation seem to have shaped the communities in the extreme environments. Deep sea consortia offer potentially valuable genes that can be explored for various applications.