Seagrass - effect on macrobenthic communities

This study investigated macroinvertebrate community composition in seagrass beds at a range of spatial scales, with an emphasis on the transition between vegetated and unvegetated sediment. Results indicated significant differences among sites and sampling locations, but contrary to many previous studies these measures were not higher inside than outside the seagrass beds. There were distinctive communities at the edge of seagrass beds at sites with high seagrass biomass, which suggests the effects of seagrass beds may extend into the unvegetated sediment. Differences in community composition were driven primarily by small changes in the relative abundance of the dominant taxa. The results of this study emphasize the need to consider the linkages between habitats in heterogeneous estuarine landscapes and how those linkages vary among sites, if the structure and functioning of macroinvertebrate communities in seagrass habitats are to be understood. Purpose: To determine the influence of seagrass beds on the diversity and abundance of macrobenthic communities.

Analysis of univariate measures of community composition (total abundance, number of species , and diversity) Multivariate analysis.

Whangamata: 175°51’45.889”E, 37°11’7.511”S Wharekawa: 175°52’48.032”E 37°6’32.462”S Whangapoua: 175°39’11.853”E, 36°44’19.116”S and 175°38’26.468”E, 36°44’6.063S”S

All data collected in January 2002

100 m2 sampling plots. 12 replicate cores taken from random positions within each sampling plot. Sieved through 1 mm mesh. Biomass of macrofauna. Measured seagrass biomass (core, 2 mm sieve and dried), sediment grain size, organic matter content and photosynthetic pigment concentration of sediments (5 replicate surficial samples at each plot). Macroinvertebrate community composition and biomass as well as sediment characteristics – 1 and 50 m inside and 1 m , 10 m, and 50 m outside seagrass bed. Data analysed with univariate and multivariate statistics. Frequency of collection: n/a

Using coarse sieve meant under representation of the smaller macrofauna, including many polychaetes and juvenile macrofauna. Gaps in collection: n/a

Sensitivity/Confidentiality: Not confidential.

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