Infaunal biodiversity patterns from Carnarvon Shelf (Ningaloo Reef), Western Australia

Abstract

Infauna are important in many ecological processes but have been rarely considered in biodiversity assessments of coral reefs and surrounding areas. We surveyed infaunal assemblages and associated environmental factors (depth, seabed reflectance, sediment characteristics) in three areas (Mandu, Point Cloates, Gnaraloo) along the Carnarvon Shelf, Western Australia. This region supports Ningaloo Reef, a relatively pristine coral reef protected by the Ningaloo Marine Park and a Commonwealth marine reserve. Macrofauna were sampled with a Smith-McIntyre grab and sieved through 500 µm. A total of 423 species and 4036 individuals was recorded from 145 grabs, with infauna accounting for 67% of species and 78% of individuals. Rare species (≤2 individuals per species) represented 42% of the total assemblage. Assemblages were significantly different among all three areas, with the most distinct recorded from the southern-most area (Gnaraloo). Although assemblages varied significantly with depth and sediment composition (mud and gravel), these relationships were weak. Results from the current study broadly quantify macrofaunal diversity in the region and identify potential spatial and environmental patterns which will help inform future marine management plans, including the provision of baseline information to assess the efficacy of protected areas in soft-sediment habitats adjacent to coral reefs.

Cross shelf benthic biodiversity patterns in the Southern Red Sea

“…Spatial patterns in the distribution and abundance of species have been reported to change significantly over cross shelf gradients 16 , however the underlying drivers of species change across these gradients has not previously been fully assessed. There has been an increasing focus worldwide on regional assessments of biodiversity that can link the role of environmental variables in structuring community composition 17 . The understanding of regional biodiversity patterns and species distribution relative to their habitat is fundamental 18 providing data that could inform science-based management approaches 6 .…”

Origin of High Density Seabed Pockmark Fields and Their Use in Inferring Bottom Currents

“…However, sediment grain-size is unlikely to be the primary determinant of infaunal species distributions, with other factors such as hydrodynamics, nutrient availability, and biological interactions being key drivers [52]. This is supported by previous analyses of polychaete assemblages in northern Australia in which sediment grain-size was shown to be weakly related to polychaete assemblages and richness [53,54]. Alternatively, as per the intermediate disturbance hypothesis [15], polychaetes may be responding to seabed disturbances associated with active pockmark fields, with successional communities being more prevalent in pockmarks as disturbances such as gas expulsion occur (Figure 15).…”

“…Alternatively, as per the intermediate disturbance hypothesis [15], polychaetes may be responding to seabed disturbances associated with active pockmark fields, with successional communities being more prevalent in pockmarks as disturbances such as gas expulsion occur (Figure 15). For example, two groups of pockmarks in the Bay of Fundy were each associated with discrete megafaunal communities, one category supporting pre-equilibrium communities and the other supporting equilibrium communities [53]. Further work is needed on this relationship, including targeted sampling within and outside individual pockmarks.…”

Comparison of sampling methods to assess benthic marine biodiversity : Are spatial and ecological relationships consistent among sampling gear?

“…Grabs and boxcorers survey a single point so overall sampling coverage is far less than sleds, trawls or dredges. Data can be extrapolated between sites, but caution should be exercised in doing this as infauna and geochemistry can vary in sediments at very fine spatial scales (Drake, 1999;Przeslawski et al 2013). Unlike data acquired from most epibenthic samplers, data acquired using grabs/box corers is quantitative (Table 1.2).…”