Variation in the population dynamics of the invasive bryozoan Membranipora membranacea along a 450-km latitudinal gradient in Newfoundland and Labrador, Canada

• Main Author: Caines, Scott Clifford Peter
• Format: Thesis
• Language: English
• Published: Memorial University of Newfoundland 2012
• Subjects: Canada; Newfoundland; Northwest Atlantic
• Online Access: https://research.library.mun.ca/6090/; https://research.library.mun.ca/6090/1/Caines_ScottCliffordPeter.pdf; https://research.library.mun.ca/6090/3/Caines_ScottCliffordPeter.pdf

The overall objective of this study was to quantify and compare seasonal (June to November) and inter-annual (2008 and 2009) variation in settlement, recruitment, and colony cover of the invasive bryozoan Membranipora membranacea on the kelp Saccharina longicruris across eight sites spanning a 450-km latitudinal gradient between the southwestern tip of Newfoundland and southeastern tip of Labrador. Thermal histories were calculated for each site to determine the extent that the observed variation was explained by sea temperature. Analysis of settlement data (Chapter II) indicated that (1) settler abundance varied both seasonally and annually with a sharp increase between August and September at warmer sites, and spatially with differences of up to three orders of magnitude between sites, (2) settler abundance and sea temperature were strongly correlated (r(2)=0.577), with maxima at mid-latitudes and minima at the northernmost and southernmost sites, and (3) exposure to waves, degree of kelp blade corrugations, and surface area of colonies of M. membranacea on kelp had little explanatory power on settler abundance across the study sites compared to sea temperature. Analysis of recruitment and colony cover data (Chapter III) indicated that (4) recruitment and colony cover varied seasonally, though variation generally decreased with increasing latitude, (5) temperature in the 76 days preceding measurements explained most [>60%] of the variation in recruitment within each month from late summer [September] to late fall [November] with the highest predictive capability (97%) in late fall, and (6) colony cover was strongly correlated (r(2)=0.524) to recruit abundance from late summer to late fall. Consistently low abundances of settlers, recruits, and colonies at the two northernmost sites suggested that M. membranacea is nearing its northern distribution limit in the northwest Atlantic. This study provides the first quantitative analysis of spatial and temporal variation in the abundance of M. membranacea in ...