Habitat fragmentation occurs worldwide and although considerable research has focused on the terrestrial environment, our knowledge on the consequences for its marine counterpart is restricted. Especially seagrass ecosystems, typically located in coastal areas are vulnerable for fragmentation due to a variety of causes. Along the Kenyan coastline which is known for its seagrass diversity, sea urchin outbreaks with concomitant seagrass overgrazing events have led to the fragmentation of once continuous T. ciliatum meadows. Information on the consequences for the associated epiphytic meiofauna is scarce. This contrasts with their pivotal role in benthic ecosystems, as they assure the energy flow from primary producers to higher trophic levels, especially to juvenile fish for which seagrass beds form nursery areas. Therefore, this study assessed the abundance and diversity of epiphytic meiofauna and more specifically of harpacticoid copepods in two continuous and two fragmented T. ciliatum meadows. Additionally, a possible effect due to a different protection status (marine park versus reserve) was tested for. Fragmentation had profound effects on the faunal densities, with significant higher densities in fragmented meadows. Additionally, a positive edge effect was found. The effect of fragmentation was more subtle on the diversity and community composition. The meiofauna community showed higher evenness in the continuous meadows, likely due to higher proportions of nematodes and nauplii. Fragmentation status had no significant effects on the copepod diversity, though higher proportions of planktonic copepods and copepodites were found in the continuous meadows. The effect of protection status was found negligible and in contrast, the local characteristics of the sampling locations were likely to explain the observed variations. Analyses at different taxonomic levels (species, genera, families) partly supported the suitability of higher taxon surrogacy for harpacticoid copepods in ecological diversity studies. In conclusion, these findings have important implications for the future selection of marine parks and reserves: selection solely based on the fragmentation status of the meadow without consideration of its local characteristics (i.e. surrounding matrix), position in the remaining habitat configuration and the processes operating at landscape scale, is unlikely to be the way forward. |
