Seagrasses
Map ID Number: Examples include 6, 9, 17, 18, 21
Location: Around mainland New Zealand and Stewart Island Approximate area:
Approximate area: Unknown
Description of habitat type:
Seagrass (Zostera capricorni) 12 is mainly intertidal in New Zealand, forming extensive monospecific beds on estuarine sandflats. The beds may extend as subtidal fringes into the shallow subtidal areas of estuaries. Permanently submerged beds of seagrass have been recorded around offshore islands (e.g. Grace and Grace 1976). Seagrass beds also occur on open coast intertidal platform reefs (e.g. Woods and Schiel 1997, Ramage and Schiel 1998, 1999).
Biological attributes:
Seagrasses are flowering plants which are restricted to shallow coastal and estuarine waters because they have high light requirements. Seagrasses possess morphological adaptations unique for submerged marine plants such as linear grass-like leaves and an extensive root-rhizome system. Seagrasses are generally considered to be highly productive, with their high biomass and production directly linked to the important roles they play in coastal and estuarine ecosystems. Recent studies have established the importance of New Zealand estuarine seagrass habitat to benthic macrofauna communities (e.g. Turner et al. 1999, van Houte-Howes et al., under review) as well as recreationally and commercially important fish species (e.g. Morrison and Francis 2001).
Criteria applied:
Species diversity; species richness; dependency for other species; trophic/functional diversity; conservation status/threat classification both nationally and globally; cultural values; degree of disturbance; special conditions and specialised organisms; habitat complexity/ diversity.
Status and management:
Seagrasses are vulnerable to human impacts such as changes in sedimentation, coastal modification, increased nutrients, and direct physical disturbance. The 1994 New Zealand Coastal Policy Statement identifies the protection of areas of significant indigenous vegetation as a national priority for the preservation of natural character of the coastal environment. Limited areas of seagrass currently receive some level of protection (e.g. Whanganui (Westhaven) Inlet and Te Angiangi marine reserves include areas of seagrass).
State of information:
Information on seagrass in New Zealand is relatively limited – in particular for permanently submerged beds. There is some information on the physiology and ecology of seagrass and some information on associated biological communities.
References and further reading:
Grace and Grace (1976), Inglis (2003), Les et al. (2002), Morrison and Francis (2001), Ramage and Schiel (1998, 1999), Turner et al. (1999), Turner and Schwarz (under review), van Houte-Howes (under review), Woods and Schiel (1997).