Faunal composition within algal mats and adjacent habitats on Likuri Island, Fiji Islands

Abstract

The faunal composition within three mono-specific algal habitats was investigated at Likuri Island, southern Viti Levu, Fiji Islands. Gracilaria maramae was the dominant alga within algal drift mat, seagrass bed, and rocky substrate habitats at the study site. This algal species exhibits two distinctive morphologies depending on whether it is attached or loose-lying. When attached to seagrass blades or rocky substrates, this alga has long straight branches stemming from a single holdfast, while detached individuals develop curled tendrils that re-attach to adjacent substrates. Re-attachment behaviour and high growth rates result in a dense mat of drift algae, which provides a suitable micro-habitat for macro-invertebrates. The sources of algal fragments that contribute to the algal mat appear to be nearby seagrass beds and rocky substrates, where this species may settle directly from spores. Storm events may detach these algae, although pulling experiments showed that the attachment to rocky substrates is 5 times stronger than the attachment to seagrass blades. Results from the macro-faunal samples indicate that the loose-lying algal mat habitat had the highest abundance and biodiversity of organisms, followed by the seagrass bed, and then the rocky substrate habitat. The ability of loose G. maramae fragments to re-attach, along with their high growth rate, may provide a unique micro-habitat for highly abundant and diverse faunal assemblages, which in turn may sustain adjacent near-shore communities. This study highlights the ecological importance of floating algal mats to coastal ecosystems, which should be considered in future management strategies throughout the Fiji Islands.

Spatial patterns in the cover and composition of macroalgal assemblages on fringing and nearshore coral reefs

“…Unlike seagrasses, which have true root systems, algae are generally unable to anchor in soft sediments (Diaz-Pulido and McCook 2008). Even the loosely attached algal mats of Padina, the galaxaurid and Dictyota found on the slopes of some platform reefs were found only on harder, more complex substrates, which may prevent them from drifting away in currents (Alfaro et al 2009). Additionally, it is likely that the higher level of turbidity found on the fringing reefs (K. Webber, pers.…”

Intertidal marine mollusks on selected coastal areas of Iligan Bay, Northern Mindanao, Philippines

“…For instance, the dog whelk Nassarius livescens was abundantly encountered on sandy seagrassbeds (Teh et al, 2014); Nassarius globosus and Nassarius luridus predominates on muddy seagrass flats (Puturuhu, Unpublished Thesis), while Nassarius albescens prefers both sandy seagrass (Alfaro et al, 2009) and rocky (Masangcay and Lacuna, 2017). The widespread distribution of nassariids within the intertidal zones is owed to their being carrion feeders or opportunistic scavengers where they often consumed bodies of dead animals as well as plants (Harasewych,1998), although some are either herbivores, detritivores/detritus feeders (Scheltema, 1964) or carnivores (Morton and Britton, 2002).…”

“…In the current study, N. globossus, N. albescens, N. luridus and N. livescens were dominant on sandy seagrass beds (station 1 and 4) as well as on sandy flat (station 3) and it is probable that these nassariids utilized the seagrass beds both for refuge and source of food and that of the sandy bottom as good supply of food. Cerithium coralium also known as coral horn was reported to occur in marine (Barnes, 2003) and estuarine (Houbrick, 1992) intertidal zones as well as on sandy substrates with the presence of the seagrassHalophila ovalis (Vohra, 1971) and on algal mats in sandy flats (Alfaro et al, 2009). This species has been reported to be deposit feeders creeping over substrates and feeding on detritus containing high algae content (Yipp, 1980).…”