Marine Debris Add-ons

 

The structure of benthic communities is a fundamental ecological property of reefs that has a large influence on the other types of organisms (e.g. fish) which might be present. Some organisms, by their biological activities, can have a large impact on community structure (e.g. sea-urchins on the presence of seaweeds). In addition, human-induced changes (e.g. accumulation of debris, changes in water quality) can alter community structure over a range of spatial scales.

 

The intent of these add-ons is to take advantage of the effort involved in laying out belt transects and recording marine debris to add value to this effort. The add-ons include censuses of benthic fauna that are either prominent on shallow subtidal reefs or are known to exert considerable influence on community structure. Echinoderms, and especially the large grazing sea-urchins, are important functional components of reefs and even relatively small changes in their abundance can alter the balance of sessile (attached) biota. Large molluscs are commonly encountered on reefs and include key grazers (e.g. the turban snails and abalone) and predators (e.g. the cart-rut snail and the triton shells). In addition to these prominent animal groups, the add-ons will target a suite of cryptic fish species that are unlikely to be seen using the fish monitoring protocol (http://uvnsw.net.au/species-descriptions).

 

A visual census method is used across the belt transects already established for the marine debris surveys (i.e. a 25 metre x 5 metre belt transect). However, the survey area is smaller and counts are only performed in a 2-metre band down the middle of each transect (i.e. 1 metre either side of the transect line). Thus, 50 m2 of benthic habitat is assessed for each transect.

 

Buddy pairs should swim down either side of the transect line

(tape measure), each covering a 1 metre wide strip. Use the tape measure to check regularly that you are searching a strip 1 metre wide. For example, place your fingertips on a metre marking on the tape measure and determine where on your upper chest 1 metre extends to. Swim slowly along the transect within 1 metre of the bottom using low impact diving techniques. Be sure to examine crevices, cracks and overhangs or the entrances to caves for species such as the Blackbanded Seaperch, sea urchins and turbinid molluscs. You will need a torch to search effectively in some complex habitats.

 

DO NOT turn over rocks or upturned pieces of coral searching for any of the species/groups listed below. While this may lead to underestimates for some species this will be consistent across all transects at all sites. Remember, UVNSW is committed to minimising impacts on marine habitats.