Late summer hyperbenthic estuarine communities: comparing permanently open and intermittently closed systems along the Otago coastline

Abstract

Few studies have compared hyperbenthic communities among estuaries, in either New Zealand or elsewhere. This study presents the results of a single late summer survey of the lower reaches of 26 estuarine systems along the Otago coastline from the Clutha River to Oamaru, comparing hyperbenthic communities among both permanently open and intermittently closed estuaries. Intermittently closed estuaries are periodically closed from the ocean because of the formation of a berm across the mouth. A total of 33 taxa were captured with mysids and amphipods, the most widespread hyperbenthic taxa, being common in both permanently open and intermittently closed Otago estuaries. The mysid, Tenagomysis novae-zealandiae, and amphipod, Paracalliope fluviatilis, were widespread, found in 74% and 68% of all estuaries sampled, respectively. In contrast, most other taxa were present in relatively few estuaries, with 17 species recorded from only 10% of estuaries. There was a significant difference in the community composition among permanently open and intermittently closed estuaries. The results highlight the potential sensitivity of New Zealand estuarine communities to management regimes that may alter their open/closed status.

Impact of Berm Breaching on Hyperbenthic Macroinvertebrate Communities in Intermittently Closed Estuaries

“…Care was taken to collect all samples in new locations, with comparable effort, intensity and to ensure a representative sample of the entire water column across all available depths (e.g. Lill et al 2010Lill et al , 2011aLill et al , 2011b. For the MBAI-2007 study, triplicate invertebrate samples were taken weekly, whereas five replicate samples were taken daily during the BACI-2008 study.…”

“…Lill et al 2010Lill et al , 2011a from the impact of berm breaching, a more intensive controlled design was used (BACI-2008), taking advantage of an artificial breaching of the Kaikorai Lagoon by the ORC. As both artificial and natural openings produce similar physicochemical changes (Dye 2005;Dye and Barros 2005a,b), it is assumed that differences between natural and artificial openings would be minimal.…”

Climate change and freshwater ecosystems in Oceania: an assessment of vulnerability and adaptation opportunities.

“…These clearly interact to produce habitats and ecosystem processes that support aquatic biodiversity. The Otago coastline forms the southeast corner of the South Island of New Zealand with a rich diversity of estuarine habitats, including permanently open estuaries and many small, intermittently open systems (Lill et al 2011). Tidally influenced freshwater wetlands and shallow lakes are also a feature of the continuously open estuaries, such as the Waihola/Waipori wetlands in the lower Taieri River catchment (Schallenberg et al 2003a;Hunt 2007).…”

“…The impacts of climate change on these estuarine systems and the species they support will vary depending on their different characteristics and dependencies (i.e., open estuaries and associated tidal freshwater lakes and wetlands or intermittently open estuarine systems) (Schallenberg et al 2010;Lill et al 2011) and the increasing effects of sea level rise in particular. Continuous high freshwater discharge from large rivers, such as the Taieri and Clutha, maintains a permanently open channel to the sea (Schallenberg et al 2003a).…”

“…The impacts of climate change (Table 1) on small, intermittently open estuaries are likely to be more complex, given these systems are more numerous and diverse (Lill et al 2011). They exist along a continuum, from ones rarely closed to rarely open (Lill et al 2011).…”