Description
In hard-bottom temperate ecosystems kelp forests can support diverse communities of organisms. Their biogenic structure can modify both longshore currents and modulate internal waves that propagate through the kelp forests. Along the southern coasts of Alaska, two species of canopy-forming kelps, Nereocystis leutkeana and Eualaria fistulosa, co-occur and have dissimilar morphologies. Their differences in morphology may affect patterns of water movement through the forests, which could have strong impacts to patterns of larval delivery and biodiversity, particularly in Kachemak Bay, Alaska which experiences large tidal fluctuations and longshore currents. The goal of our research was to determine how currents are affected by canopy type and to determine if larval delivery of invertebrates and benthic biodiversity differ between canopy types. Differences in current modulation were found between kelp forest types and both larval and benthic biodiversity differed among sites and between kelp forest types. The greatest current modulation was observed in the Nereocystis luetkeana kelp forests. When the larval settlement data were integrated over the 4 week study period there was no difference in larval settlement, however higher resolution analyses showed that larval settlement differed among the sites, kelp forest types, and location within or outside of the kelp forest canopy. Our results suggest that ongoing monitoring programs of kelp forest distribution in the Kachemak Bay Research Reserve should include data on kelp forest type as well as extent.
