Influence of environmental factors on macrofoulant assemblages on moored buoys in the eastern Arabian Sea

Abstract

Factors governing the distribution of organisms in the pelagic ocean are understudied. In this paper we describe environmental parameters and macrofouling assemblages on 11 buoys deployed in the Arabian Sea for an average duration of 322 days. Macrofoulants on all the mooring components extending from the sea-surface to a depth of 1800-4300 m were documented. Role of temperature, salinity, dissolved oxygen, biological productivity and zooplankton community in governing the macrofoulant distribution are described. Species composition, vertical zonation and wet biomass exhibited significant spatial variations. Lepas anatifera constituted more than 90% of foulant wet biomass on all moorings. Assemblages in the southeastern (SEAS), east-central (ECAS) and northeast (NEAS) regions were distinct. Density of L. anatifera on surface buoys were low in SEAS (0.2±0.09 no./cm 2 ), high in ECAS (0.32±0.11 no./cm 2 ) and moderate in NEAS (0.23±0.04no./cm 2 ). Macrofoulants were observed up to a depth of 75 m in SEAS, 130 m in ECAS and 120 m in NEAS. The depth profile of macrofoulant assemblages on moorings could be related to the prevalent hypoxic condition. Vertical profiles of wet biomass on all moorings exhibited subsurface maxima at depth ranging from 10 to 20 m, consequent to the abundance of L. anatifera in a thermally stable depth of water column, wherein diurnal and semidiurnal temperature variability was minimal. We attribute the observed variation in fouling assemblages to dissolved oxygen levels, salinity and diurnal variability in temperature and salinity.

Biofouling on mooring systems in the Talaud and Halmahera Seas, Indonesia

“…Apart from being a nuisance, we could study the distribution of deep-sea organisms from biofouling on the mooring systems. In addition, sessile organism assemblage on mooring systems can also give knowledge regarding their habitat and ecosystem health [3]. Temperature, exposure to light, nutrients, pressure, type of substratum, and individual species dispersion have all been identified as factors influencing the spread of sessile communities [4,5].…”

“…Temperature, exposure to light, nutrients, pressure, type of substratum, and individual species dispersion have all been identified as factors influencing the spread of sessile communities [4,5]. On the other hand, invertebrate species that dominate sessile populations below the photic zone rely on exogenous organic material for nourishment [3,6,7,8]. Futhermore, sessile organism assemblages on the mooring systems and other offshore instrument platforms (e.g., petroleum platforms, under-sea cables, wind farms, test panels) displayed significant regional heterogeneity and vertical zoning [4,9,10,11,12,13].…”