Foraminiferal record of human impact

Collaborators: Mark Horrocks (Microfossil Research, Auckland); George Scott (GNS, Lower Hutt).

Building on our previous studies, we undertook studies to develop more precise relationships between modern estuarine and sheltered harbour foraminiferal distribution patterns and: freshwater runoff and salinity; sediment grain-size and runoff from land; heavy metal pollution from industry and marinas; and high nutrient levels from sewerage outfalls, intense marine aquaculture and introduced marine species.

The goal of this research strand is to provide a NZ-wide synthesis of foraminiferal faunas as indicators of clean and impacted coastal marine environments, for use in documenting and monitoring human impacts on these fragile ecosystems, and in some instances their recovery.

The first studies (2002-2003) were undertaken in the Waitemata Harbour, Auckland and resulted in the development of a Confinement Index, which provides proxy values for salinity based on foraminiferal census counts. In these studies we have found that increased freshwater runoff and decreased pH have been the most significant factors in producing faunal changes, and that sediment grain-size, nutrients and heavy metal pollution have had little impact in the coastal waters around New Zealand's largest city.

Studies in the Mangere arm of Manukau Harbour recorded the impacts of freezing works effluent up to 1960, and the more widespread impact of discharges from the Mangere Sewerage Treatment Plant after 1960.

Study areas:
a. Impact of nutrients (sewage) on the Manukau Harbour, Auckland - Andrew Matthews, published, 2005.
b. Impact of freshwater on the upper Waitemata Harbour, Tamaki Estuary and Panmure Basin, Auckland - published 2004, 2006.
c. Impact of freshwater, sediment runoff and nutrients (sewerage, oyster farming) on the Mahurangi Harbour - published, 2007.
d. Impact of mussel farming on underlying soft sediment biotas in Firth of Thames and Great Barrier Island - commenced 2005; abandoned 2007.
e. Impact of introduced chord grass (Spartina) and Asian date mussels (Musculista) on estuarine biotas. Raglan Harbour, Firth of Thames, Mahurangi Harbour, Tamaki Estuary, Kaipara Harbour - published 2008.
f. Impact of ocean acidification in estuaries. Whanganui Inlet, NW Nelson; Tautuku Estuary, SE Otago – internal report available on request, 2010.

Publications:

• Hayward, B.W., Grenfell, H.R., Sabaa, A.T., Morley, M.S., 2008. Ecological Impact of the introduction to New Zealand of Asian Date Mussels and Cordgrass - the Foraminiferal, Ostracod and Molluscan Record. Estuaries and Coasts 31: 941-959.
• Grenfell, H.R.,Hayward, B.W. and Horrocks, M., 2007. Foraminiferal record of ecological impact of deforestation and oyster farms, Mahurangi Harbour, New Zealand. Marine and Freshwater Research 58: 475-491.
• Hayward, B.W., Grenfell, H.R., Sabaa, A., Morley, M.S. and Horrocks, M., 2006. Impact and timing of increased freshwater runoff into sheltered harbour environments around Auckland City, New Zealand. Estuaries and Coasts, 29: 165-182.
• Matthews, A.; Grenfell, H. R.; Hayward, B. W.; Horrocks, M. 2005: Foraminiferal record of sewage outfall impacts on the inner Manukau Harbour, Auckland, New Zealand. New Zealand Journal of Marine and Freshwater Research, 39: 193-215.
• Hayward, B.W.; Grenfell, H.R.; Nicholson, K.; Parker, R.; Wilmhurst, J.; Swales, A.; Sabaa, A.T., 2004. Foraminiferal record of human impact on intertidal estuarine environments in New Zealand's largest city. Marine Micropaleontology 53 : 37-66.
• Hayward, B.W.; Scott, G.H.; Grenfell, H.R.; Carter, R.; Lipps, J.H. 2004: Techniques for estimation of tidal elevation and confinement (~salinity) histories of sheltered harbours and estuaries using benthic foraminifera: Examples from New Zealand. The Holocene 14(2): 218-232