transport focus largely on: (1) where they go and (2) where they came from (Levin
2006). Assessments of temporal and spatial abundance patterns of pelagic larval
stages are relevant for understanding dispersal strategies, spatial connectivity and
recruitment dynamics (Williams and García Sais 2010). Larval abundance measurements is a challenging undertaking for echinoderms due to their small size,
relatively long pelagic larval life, potential for patchy distributions and the
dynamic environment in which they live in (Williams et al. 2009). Larval
community characterizations are typically incomplete and may underestimate
abundance, especially when using large mesh diameters such as C202 lm for
plankton tows (Williams and García Sais 2010). There are several studies of
coastal zooplankton communities of Caribbean systems (Reeve 1970; Youngbluth
1980; McWilliam et al. 1981; Yoshioka et al. 1985) however, these studies do not
report on echinoderm larvae from plankton sampling.
The colonization of benthic habitats by marine organisms with planktonic lifestages involves three phases: planktonic development and dispersal, habitat
selection and settlement (Keough and Downes 1982). Settlement rate is defined as
the rate at which planktonic larvae of benthic organisms establish permanent
contact with the substrate. Trying to identify sources and/or sinks of larvae is
important to understanding supply to populations (Miller and Emlet 1997). Marine
invertebrate larvae may navigate to suitable settlement sites by responding to
gradients of environmental stimuli (Kingsford et al. 2002). Recruitment, which is
the fourth phase, includes the survival of the organism until observable by an
observer (Keough and Downes 1982). Recruitment is a key mechanism shaping
and structuring reefal communities (Cameron and Schroeter 1980). Recruitment
rather than reproductive output is the key concept for marine species demography
and is one of the main determinants of spatial and temporal variations in population sizes (Cowen et al. 2000). Larval availability, substrate selection and
juvenile mortality are factors that influence recruitment to a population. There
have been only a few larval and recruitment studies of echinoderms in Puerto Rico.
Most of these studies focused on Echinoidea.
Studies on the Reproduction, Larval Biology, Settlement, and Recruitment
of Lytechinus variegates (Lamarck), Echinometra viridis (Agassiz),
Echinometra lucunter (Linnaeus), and Tripneustes ventricosus (Lamarck)
Cameron (1983, 1986) measured the reproduction, larval abundance, and size
distribution for Lytechinus variegatus, Echinometra viridis, E. lucunter and
Tripneustes ventricosus in La Parguera, Puerto Rico (Fig. 14.2). The mean gonad
index of L. variegatus ranged from 0.8 in October 1981 to 7.8 in October 1983.
The higher gonad indices occurred during the late summer and early fall months
for L. variegatus and Echinometra spp. This is when the sea surface temperatures
were at their highest. Spawning occurred eight times ranging over all seasons of
the year for L. variegatus. The gonad indices for Echinometra spp. reached a peak
in August 1983 (10.0). The degree of synchrony was much greater for
442
S. M. Williams et al.
2006). Assessments of temporal and spatial abundance patterns of pelagic larval
stages are relevant for understanding dispersal strategies, spatial connectivity and
recruitment dynamics (Williams and García Sais 2010). Larval abundance measurements is a challenging undertaking for echinoderms due to their small size,
relatively long pelagic larval life, potential for patchy distributions and the
dynamic environment in which they live in (Williams et al. 2009). Larval
community characterizations are typically incomplete and may underestimate
abundance, especially when using large mesh diameters such as C202 lm for
plankton tows (Williams and García Sais 2010). There are several studies of
coastal zooplankton communities of Caribbean systems (Reeve 1970; Youngbluth
1980; McWilliam et al. 1981; Yoshioka et al. 1985) however, these studies do not
report on echinoderm larvae from plankton sampling.
The colonization of benthic habitats by marine organisms with planktonic lifestages involves three phases: planktonic development and dispersal, habitat
selection and settlement (Keough and Downes 1982). Settlement rate is defined as
the rate at which planktonic larvae of benthic organisms establish permanent
contact with the substrate. Trying to identify sources and/or sinks of larvae is
important to understanding supply to populations (Miller and Emlet 1997). Marine
invertebrate larvae may navigate to suitable settlement sites by responding to
gradients of environmental stimuli (Kingsford et al. 2002). Recruitment, which is
the fourth phase, includes the survival of the organism until observable by an
observer (Keough and Downes 1982). Recruitment is a key mechanism shaping
and structuring reefal communities (Cameron and Schroeter 1980). Recruitment
rather than reproductive output is the key concept for marine species demography
and is one of the main determinants of spatial and temporal variations in population sizes (Cowen et al. 2000). Larval availability, substrate selection and
juvenile mortality are factors that influence recruitment to a population. There
have been only a few larval and recruitment studies of echinoderms in Puerto Rico.
Most of these studies focused on Echinoidea.
Studies on the Reproduction, Larval Biology, Settlement, and Recruitment
of Lytechinus variegates (Lamarck), Echinometra viridis (Agassiz),
Echinometra lucunter (Linnaeus), and Tripneustes ventricosus (Lamarck)
Cameron (1983, 1986) measured the reproduction, larval abundance, and size
distribution for Lytechinus variegatus, Echinometra viridis, E. lucunter and
Tripneustes ventricosus in La Parguera, Puerto Rico (Fig. 14.2). The mean gonad
index of L. variegatus ranged from 0.8 in October 1981 to 7.8 in October 1983.
The higher gonad indices occurred during the late summer and early fall months
for L. variegatus and Echinometra spp. This is when the sea surface temperatures
were at their highest. Spawning occurred eight times ranging over all seasons of
the year for L. variegatus. The gonad indices for Echinometra spp. reached a peak
in August 1983 (10.0). The degree of synchrony was much greater for
442
S. M. Williams et al.