Submitted and accepted for the Symposium of Contemporary Conservation Practice (SCCP) 2016 as a poster presentation.

1. Title: Crabs, heavy metals and near future ocean acidification – what do we know?
Durban Harbour, Richards Bay Harbour and Mlalazi estuary are part of KwaZulu-Natal estuarine
systems. Durban and Richards Bay, like most estuarine harbours, are persistently subjected to
anthropogenic activities (intense urbanization and industrialization) as well as expansion of
commercial shipping resulting in bioaccumulation of pollutants i.e. heavy metals, chemical and
organic pollutants. The uMlalazi estuary on the other hand is situated in a coastal nature reserve
and the watershed is in a lower population density area and as a consequence is less prone to
anthropogenic effects. Crabs, as both predator and prey, form an important component of marine
food webs. They are mostly benthic with restricted mobility and are especially sensitive to
pollution because they reside on the substrate where chemical contaminants accumulate. Crabs
accumulate pollutants including metals, resulting in biological alterations from molecular to tissue
level depending on pollutant concentrations and duration of exposure. Pollutants may therefore be
bioaccumulated in crabs resulting in several orders of magnitude higher than those of the
surrounding water, with further biomagnification in the food chain to higher trophic levels,
including human consumers.
The background levels of heavy metals (Pb, Cd, Zn and Cu) in tissues (hepatopancreas, gills,
muscle and exoskeleton) of sand bubbler crabs (Dotilla fenestrata), sediments and water were
investigated through nitric acid digestion and metal analysis was done using Inductive Coupled
Plasma Mass Spectrometry (ICP-MS). Crabs were also exposed to varying concentrations of Cd
and Pb under near-future pH for 96 hours to replicate heavy metal uptake under predicted 2030
levels of ocean acidification. Acute toxicity test (lethal concentration) was determined after 96
hours of exposure using a range finder test to determine the concentration of metals in combination
with varying pH. Crabs were dissected after 96 hours exposure to determine heavy metal
bioaccumulation in tissues as a result of interactive reaction of metal solutions and pH. Results
obtained from this study will contribute to our understanding of how crabs respond to heavy metal
uptake in the context of global climate change, more specifically with respect to near-future ocean
acidification.