Tidal migration influences the zonation of grazing snails (Turbo smaragdus) in a mangrove-seagrass estuary, Northern New Zealand
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The zonation of mobile species, such as grazing snails, may be influenced by migration patterns, which often are missed if the population is not sampled within the appropriate temporal scales (i.e., tidal cycles, diurnal periods, seasons). Aspects of community ecology, especially abundance, biodiversity, and habitat preferences, are better described when the mobility of different species or group of organisms also are investigated. The effect of migration on the density and size-frequency distribution of a dominant intertidal grazer (Turbo smaragdus) was investigated across four habitats (mangrove tree, pneumatophore, algal aggregation, and seagrass bed) during emersion and immersion periods at Matapouri Estuary, northern New Zealand, in August 2004 and March 2005. Snails were marked and recaptured to identify their specific movements across the four zones during high and low tide periods. Results from the population surveys and the marked-recaptured experiments indicate that snails migrate upward during high tide and do wnward during low tide. These snail movements appear to be related to improved feeding activity during tidal inundation within macroalgal aggregations in the pneumatophore and algal zones. Large snails (up to 48 mm in width) were predominant in the highest zone among the mangrove trees, where they appear to feed on filamentous algae and microalgae that cover the sediment and plant surfaces in this area. Differences in snail density and sizes between the two sampling months were attributed to reproductive patterns of this species, which result in about 30% more snails (mostly juveniles) during peak reproduction in March.
KeywordsMacroalgae High Tide Tidal Cycle Rocky Shore Tidal Inundation
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- Cresse, R. G. 1988. Ecology of molluscan grazers and their interactions with marine algae in north-eastern New Zealand: A review.New Zealand of Marine and Freshwater Research 22:427–444.Google Scholar
- Davidson, I. C., A. C. Crooks, andD. K. A. Barnes. 2004. Macrobenthic migration and its influence on the intertidal diversity dynamics of a meso-tidal system.Marine Biology 145:833–842.Google Scholar
- Edwards, M. F. 1982. Gastropod-algal interactions in the intertidal region. M.Sc. Thesis, University of Auckland, Auckland, New Zealand.Google Scholar
- Grange, K. R. 1974. Population structure, breeding cycles and larval development in some trochid and turbinid gastropods. M.Sc. Thesis, University of Auckland, Auckland, New Zealand.Google Scholar
- Hutchinson, N. andG. A. Williams. 2003. An assessment of variation in molluscan grazing pressure on Hong Kong rocky shores.Marine Biology 142:495–507.Google Scholar
- Robinson, L. 1992. Population and reproductive ecology ofTurbo smaragdus in the Kaikoura region M. Sc. Thesis, Department of Zoology, University of Canterbury, Canterbury, New Zealand.Google Scholar
- Town, J. C. 1981. Prey characteristics and dietary composition in intertidalAstrostole scabra (Echinodermata: Asteroidea).New Zealand Journal of Marine and Freshwater Research 15:69–80.Google Scholar
- Walker, N. 1998. Grazing in the intertidal zone: Effects of the herbivorousTurbo smaragdus on macroalgae assemblages M.Sc. Thesis, Department of Zoology, University of Canterbury, Canterbury, New Zealand.Google Scholar
- Walsby, J. R. 1977. Population variations in the grazing turbinidLunella smaragda (Mollusca: Gastropoda).New Zealand Journal of Marine and Freshwater Research 11:211–238.Google Scholar