TITLE:
Demographics and Population Dynamics Project the Future of Hard Coral Assemblages in Little Cayman
AUTHORS:
Kristi A. Foster, Greg Foster
KEYWORDS:
Caribbean Coral, Size Class Transitions, Vital Rates, Recovery Projections, Little Cayman
JOURNAL NAME:
Open Journal of Marine Science,
Vol.8 No.1,
January
31,
2018
ABSTRACT:
Individual hard coral colonies from four representative reef sites around Little
Cayman were surveyed yearly between 2010 and 2015, a period of non-disturbance
between two elevated seawater temperature anomalies. Photographic
censuses produced 7069 annual transitions that were used to describe the demographics
(size class frequencies, abundance, area cover) and population
dynamics under non-disturbance environmental conditions. Agariciids, Porites
asteroides, and Siderastrea radians have replaced acroporids as the predominant
massive corals. Recruitment rates were generally low (2), except for a fourfold recruitment pulse of S. radians that occurred in
2011. On average, 42% of coral recruits survived their first year but only 10%
lived longer than four years. Temporal comparisons allowed correction factors
to be calculated for in-situ methods that overestimate recruitment of colonies
≤2 cm in diameter and overlook larger colonies. Size class transitions
included growth (~33%), stasis (~33%), partial mortality (10% - 33%), and
whole colony mortality, which decreased with increasing colony size (typically
30 cm2). Transition matrices indicated
that Little Cayman assemblages have declining hard coral populations (λ 150 cm2 surface areas, live area cover may remain relatively
stable. Projection models indicated that downward population trends would
be exacerbated even by mild disturbance (5% - 10% mortality) scenarios. The
fate of hard corals on Little Cayman’s reefs was determined to be heavily dependent
on the health and transitions of agariciid colonies. Conservation
strategies that currently focus on restoration of Caribbean acroporids should
be expanded to include agariciids, which were previously considered “weeds”.