A poor understanding of responses of corals to sediment disturbances can result in inappropriate management of dredging projects that may lead to preventable coral mortality or unnecessarily high costs from down-time and delays in dredging operations. There are many examples of dredging operations near coral reefs where inadequate management has contributed to significant damage to reefs and mortality of corals (Table 1). Conversely, exaggerated (over-conservative) thresholds used for predicting levels of coral mortality from dredging can lead to unrealistically
high levels of predicted coral mortality over large areas of presumed impact. A review of ten recent (large) capital dredging projects near coral reefs in the Akt inhibitor Pilbara region (Western Australia) described how conditions governing environmental controls and monitoring requirements have become increasingly comprehensive, prescriptive and onerous since 2003 (Hanley, 2011). However, in none of these case studies was there evidence of any breach (non-compliance) of the permitted levels of impacts on corals. In fact, observed mortality of corals in these projects typically was far below predictions and could in many cases be attributed to other
factors not related to dredging (e.g. cyclonic events and thermal bleaching). click here The review warned about selleckchem the consequences of such routine overestimation of dredging impacts to corals, including the misinformation of the public, unrealistically large offset packages and unnecessarily large monitoring and baseline programs to areas well outside the real range of impacts (Hanley, 2011). These examples from Western Australia, along with the various case studies summarised in Table 1, clearly
demonstrate the need for strengthening capacity in predicting and managing impacts of dredging through thorough literature reviews, a critical evaluation of past dredging projects near corals, and targeted experimental research (Lavery and McMahon, 2009). The main effects of dredging and port construction on corals—besides direct physical removal, damage or burial—include temporarily increased turbidity and enhanced sedimentation. In order to understand how corals are affected by enhanced turbidity and sedimentation, it is important to first gain some basic understanding on how corals function. With the exception of free-living species, corals—once settled—are sessile organisms (Hoeksema, 1988, Hoeksema, 1993, Hubmann et al., 2002 and Hoeksema and de Voogd, 2012). As they cannot move away from unfavourable conditions, growth-form and physiological changes regulate their interactions with the environment.