Aquatic Environment and Biodiversity Annual Review 2012

AEBAR 2012: Ecosystem effects: Land-based effects
outlets or associated with areas of intensive agriculture or horticulture. Sediment production has been
mapped around the country and is greatest around the west coast of the South Island and the East
coast of the North Island (Griffiths and Glasby 1985, Hicks and Shankar 2003, Hicks et al. 2011).
Notably the catchments where improved land management may result in the biggest changes to
sediment delivery to coastal environments are likely to be the Waiapu and Waipaoa river catchments
on the East coast of the North Island. In addition to this, the sensitivity of receiving environments is
also likely to differ; this will be covered in subsequent sections.
A MPI funded survey of scientific experts (MacDiarmid et al. 2012) addressed the vulnerability to a
number of threats of marine habitat types within the New Zealand’s Territorial Sea and Exclusive
Economic Zone (EEZ). Each vulnerability score was based on an assessment of five factors including
the spatial scale, frequency and functional impact of the threat in the given habitat as well as the
susceptibility of the habitat to the threat and the recovery time of the habitat following disturbance
from that threat. The study found that the number of threats and their severity were generally
considered to decrease with depth, particularly below 50m. Reef, sand, and mud habitats in harbours
and estuaries and along sheltered and exposed coasts were considered to be the most highly threatened
habitats. The study also reported that over half of the twenty-six top threats fully, or in part, stemmed
from human activities external to the marine environment itself. The top six threats in order were:
1. ocean acidification,
2. rising sea temperatures resulting from global climate change,
3 rd equal bottom trawling fishing,
3 rd equal increased sediment loadings from river inputs
5 th equal change in currents from climate change
5 th equal increased storminess from climate change
The reader is guided to MacDiarmid et al. (2012) for more detail including tables of threats-by-habitat
and habitats-by-threat. Climate change and ocean acidification, although they can be considered landbased
effects, are covered under the Chapters in this document called “New Zealand Regional climate
and oceanic setting” and “Biodiversity”.
The protozoan Toxoplasma gondii has been identified as the cause of death for 7 of 28 Hector’s and
Maui’s dolphins examined since 2007 (W. Roe, Massey University, unpubl. data, 31 July 2012).
Land-based runoff containing cat faeces is believed to be the means by which Toxoplasma gondii
enters the marine environment (Hill & Dubey 2002). A Hectors dolphin has also tested positive for
Brucella abortus (or a similar organism) a pathogen of terrestrial mammals that can cause late
pregnancy abortion, and has been seen in a range of cetacean species elsewhere 29 .
10.3.1. Completed research
A MPI funded project (IPA2007/07) reviewed the impacts of land based influences on coastal
biodiversity and fisheries (Morrison et al. 2009). This review used a number of lines of evidence to
conclude that in this context, sedimentation is probably New Zealand’s most important pollutant. The
negative impacts of sediment include decreasing efficiency of filter-feeding shellfish (such as cockles,
pipi, and scallops), reduced settlement success and survival of larval and juvenile phases (e.g., paua,
kina), and reductions in the foraging abilities of finfish (e.g., juvenile snapper). Indirect effects
include the modification or loss of important nursery habitats, particularly biogenic habitats (greenlipped
and horse mussel beds, seagrass meadows, bryozoan and tubeworm mounds, sponge gardens,
29 http://www.doc.govt.nz/Documents/conservation/native-animals/marine-mammals/maui-tmp/mauis-tmp-
discussion-document-full.pdf
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