MEPS 344:95-106 (2007)  -  DOI: https://doi.org/10.3354/meps06924

ABSTRACT: Settlement is a critical life-history stage for benthic invertebrates with a planktonic larval form, and is important for understanding mechanisms of larval supply and population dynamics. We examined spatial (metre to kilometre scales) and temporal (weekly to yearly scales) patterns in abundance of settlers of the introduced bryozoan Membranipora membranacea on the numerically dominant kelp Saccharina longicruris, at 2 sites in St. Margarets Bay, Nova Scotia, Canada. Relationships between patterns in settlement and indices of the temperature regime, such as average weekly temperature, temperature fluctuations, water column stratification and thermal history (growing degree-day) were determined using multiple linear regressions. Although settler abundance varied interannually, it was highest in early autumn, and was generally higher at depth (12 and 8 m) than in the shallows (4 m). Abundance was an order of magnitude greater after a significantly warmer winter. Growing degree-day accounted for up to 81% of the variability in settler abundance, whereas average temperature, temperature fluctuations and stratification were less important. The strong positive relationship between thermal history and settlement of this ecologically important species suggests that abundance of established introduced marine species may increase with the increased temperatures predicted to result from climate change.

KEY WORDS: Larval settlement · Temperature · Thermal history · Stratification · Bathymetric patterns · Benthic invertebrates · Introduced species · Climate change