- Dredging results in the short term degradation of animals, vegetation and
microbial communities that live in the dredged sediment. This reduces the estuary's
capacity for nutrient cycling, primary production and habitat provision and can
have flow on effects up the food web. Though these effects tend to be short lived,
in some cases they may trigger long-term changes. (Larkum and West, 1990; Lewis
et al, 2001; Thrush and Dayton, 2002; Lohrer and Wertz, 2003; da Silva et al,
2004; Waycott et al, 2004; Ohimain et al; 2005)
- Changes in channel profile caused by dredging can increase tidal area,
wave height and water velocity, resulting in bank erosion. Eroding banks threaten
mangroves and other mudbank communitites and can lead to increased turbidity.
Suspended sediment in the water column blocks light, reducing benthic primary
productivity and inhibits the ability of benthic plants to recover from impacts
of dredging. (Pringle, 1989; Larkum and West, 1990; Lewis et al, 2001; Rasheed
and Balchand; 2001; Lohrer and Wertz, 2003; Sampson et al, 2005)
- Dredging exposes anaerobic layers of sediment, potentially disturbing and
remobilising toxic sediments, releasing contaminants. This has implications for
water quality. (Linkov et al, 2001; Thibodeaux and Duckworth, 2001; Van Den Berg,
2001; Nayar et al, 2004)
- Dredge spoil needs to be deposited somewhere, though this could be deemed
habitat creation, it can smother existing habitats and frequently contains contaminants
which often move and bioaccumulate through the food web. The impacts of dredge
spoil disposal can range from short term to long term (Linkov et al, 2001; Smith
and Rule, 2001; National Ocean Disposal Guidelines for Dredged Material, 2002;
Fredette and French, 2004)
- Changes to tidal range and wave action can result in mangrove encroachment
into saltmarsh areas (Saintilin and Williams, 1999)
- da Silva, J.F., Duck, R.W. & Catarino, J.B. 2004, "Seagrasses and sediment
response to changing physical forcing in a coastal lagoon", Hydrology and Earth
System Sciences, vol. 8, no. 2, pp. 151-159.
- Larkum, A.W.D., West, R.J. 1990 Long-term Changes of Seagrass Meadows in Botany
Bay, Australia Aquatic Botany, 37 (1): 55-70.
- Lewis, M.A., Weber, D.E., Stanley, R.S. & Moore, J.C. 2001 Dredging impact
on an urbanized Florida bayou: effects on benthos and algal-periphyton, Environmental
Pollution, vol. 115, no. 2, pp. 161-171.
- Linkov, I., von Stackelberg, K.E., Burmistrov, D. & Bridges, T.S. 2001, Uncertainty
and variability in risk from trophic transfer of contaminants in dredged sediments,
Science of the Total Environment, vol. 274, no. 1-3, pp. 255-269.
- Lohrer, A.M. & Wetz, J.J. 2003, Dredging-induced nutrient release from sediments
to the water column in a southeastern saltmarsh tidal creek, Marine Pollution
Bulletin, vol. 46, no. 9, pp. 1156-1163.
- Nayar, S., Goh, B.P.L. & Chou, L.M. 2004, Environmental impact of heavy metals
from dredged and resuspended sediments on phytoplankton and bacteria assessed
in situ mesocosms, Ecotoxicology and environmental safety, vol. 59, no. 3, pp.
- Ohimain, E.I., Imoobe, T.O.T. Benka-Coker, M.O. 2005, The impact of dredging
on macrobenthic invertebrates in a tributary of the Warri River, Niger delta,
African Journal of Aquatic Science, vol. 30, no.1, pp. 49-54(6).
- Pringle, A.W. 1989 The history of dredging in Cleveland Bay, Queensland and
its effect on sediment movement and on the growth of mangroves, corals and seagrass,
- Rasheed, K. & Balchand, A.N. 2001, Environmental studies on impacts of dredging,
International Journal of Environmental Studies, vol. 58, no. 6, pp. 703-725.
- Sampson, J., Easton, A., Singh, M., 2005, Modeling the effect of proposed channel
deepening on the tides in Port Phillip Bay, Australian & New Zealand Industrial
and Applied Mathematics Journal, 46 (E) p C888-C901.
- Smith, S.D.A. & Rule, M.J. 2001, "The Effects of Dredge-Spoil Dumping on a
Shallow Water Soft-Sediment Community in the Solitary Islands Marine Park, NSW,
Australia", Marine Pollution Bulletin, vol. 42, no. 11, pp. 1040-1048.
- Thibodeaux, L.J. & Duckworth, K.T. 2001, The Effectiveness of Environmental
Dredging: A Study of Three Sites, Remediation, vol. 11, no. 3, pp. 5-34.
- Thrush, S.F., Dayton, P.K., 2002, Disturbance to marine benthic habitats by
trawling and dredging: Implications for marine biodiversity, Annual Review of
Ecology and Systematics, 33, p449-474.
- Van Den Berg, G.A., Meijers, G.G.A., Van Der Heijdt, L.M. & Zwolsman, J.J.G.
2001, Dredging-related mobilisation of trace metals: A case study in the Netherlands,
Water research, vol. 35, no. 8, pp. 1979-1986.
- Waycott, M., Longstaff, B.J. & Mellors, J. 2005, "Seagrass population dynamics
and water quality in the Great Barrier Reef region: A review and future research
directions", Marine Pollution Bulletin, vol. 51, no. 1-4, pp. 343-350.