J. mar. biol. Ass. U.K. (2012) Printed in Great Britain
SURVEY TECHNIQUES USED AND DIFFERENCES IN SETTLEMENT IN THE STUDY OF MARINE BIODIVERSITY Barnes L. Falmouth Marine School Laboratories, University of Plymouth, Cornwall TR11 3QS UK This study in particular looks at individual species count of all species recorded on the panels to determine whether there is a difference between abundance of species and biodiversity at commercial and recreational sites. The data was collected fortnightly to record settlement of species without removing the panels. Three from each site were then removed and returned to the laboratory for sampling and recording species count. Seasonal recruitment of a species is an important factor to consider, (Underwood 1994), especially when there are time constraints.
Keywords: Abundance; Settlement; Biodiversity; Seasonal recruitment
INTRODUCTION Biodiversity is measured by species dominance and abundance (Magurran 1998), with marine biodiversity relating to the diversity of all areas from the coastline to the open ocean (Queffelec 2009). Many experiments have been conducted to record the abundance and variety of benthic species in estuarine communities and on different substrates. Two of the most recent looked at the settlement of fouling species on offshore wind farm platforms (Wilhelmsson 2008), and the settlement of sessile fouling communities on structures in the Baltic Sea (Qvarfordt 2006). Alongside these studies, one of the concepts to be looked at in recent years is the idea of succession, which in the past has usually been applied to the terrestrial environment (Clements 1936). The idea being that different species will colonise a certain area or substrate at different stages, each allowing for the other, eventually forming a community of co-existing species, ‘a climax community’ (Odum 1969). As stated by Underwood & Denley 1984, ‘ The settlement of invertebrates from the plankton is one of the most important areas to look at for succession to occur.’ Succession within a harbour community can be difficult to measure as there are a number of fouling species known to colonise this type of substrate and others which are not common. A previous experiment conducted found that the solitary ascidian Ciona intestinalis, when in the presence of the fouling species Tubularia larynx, was known to become more abundant (Schmidt 1983). The same study found ‘blooms’ of Ascidiella aspersa, another ascidian species native to the British Isles occurring, with both species out-competing everything else. It is thought the hydroid T. larynx encourages these solitary species by creating the ideal conditions for their growth (Dean & Hurd 1981). Due to factors like this identification and succession rate of native species can be made more difficult.