Scales of Variability in Larval Settlement Within the Channel Islands National Marine Sanctuary and Along the Mainland Coast
Schroeter SC, Page HM, Dugan JE, Culver CS, Steele B, Guiterrez R, Richards JB, Kushner D. 2010. Scales of Variability in Larval Settlement Within the Channel Islands National Marine Sanctuary and Along the Mainland Coast. J9C706004. Santa Barbara, CA
We explored variability in the settlement rates of sea urchins (Strongylocentrotus franciscanus, S. purpuratus), and rock crabs (Cancer spp.) across different spatial (100’s of m to 90 km) and temporal (biweekly to decadal) scales adjacent to Santa Cruz and Santa Rosa Islands and along the Santa Barbara mainland coast. Here, we refer to "settlement" as a best estimate of the abundance of small stages of invertebrates recently settled from the plankton. Settlement was measured using two types of collectors: wood-handled scrub brushes and "tuffy" scrub pads attached 1 to 2 m off the bottom either on buoyed mooring lines at stations inside and outside of 2 marine protected areas (MPAs) at the islands or suspended from piers. Island samples (brushes and tuffys) were retrieved and replaced using methods that we developed enabling surface-based retrieval. Larval settlement varied dramatically on a scale of 100’s of meters within and across MPA boundaries. For both red and purple urchins, average settlement at the Santa Cruz and Santa Rosa Island sites in 2006 was an order of magnitude higher than average settlement at mainland sites in 2006 and also higher than the historical mainland average (based on a 16 year time series). Although more data are needed from the islands, our results suggest that local and regional scale variability in larval settlement could have important implications for MPAs and for sampling design. Areas with lower settlement rates may take longer to recover depleted populations or be less suitable for restoration efforts based on natural replenishment than areas with greater settlement.
- Type
- Published Report
- Authors
- Schroeter, Stephen; Page, Henry; Dugan, Jenifer; Culver, Carolynn; Steele, Bruce; Guiterrez, Rick; Richards, John; Kushner, David
- Date of Issue
- 2010
- Units
- CHIS
- Keywords
- benthic recruitment, Channel Islands, Invertebrate settlement, rock crab, sea urchin, spatial and temporal variability