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Cryptic Bryozoa, leeward fringing reef of Bonaire, Netherlands Antilles, and their paleoecological application
- David R. Kobluk, Roger J. Cuffey, Shirley S. Fonda, Mary A. Lysenko
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- Journal of Paleontology / Volume 62 / Issue 3 / May 1988
- Published online by Cambridge University Press:
- 02 September 2016, pp. 427-439
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A collection of 6,151 bryozoan colonies (two cyclostome species from two families, and 73 cheilostome species from 30 families) from the leeward fringing reef of Bonaire, Netherlands Antilles, is largely, but not entirely, of Caribbean affinities, with some links to Indo-Pacific populations. The bryozoans from Bonaire show some relation to water depth at species and higher taxonomic levels, but these relations are not clear-cut. Many of the species are found through all or most of the 73 meter depth range sampled, but a few are limited to shallow water, and some to deeper water. At a higher taxonomic level, some families (e.g., Calloporidae, Bugulidae, Smittinidae) include wide depth-ranging species, shallow-water species, and deep-water species; this indicates some divergence between species and family-level depth distributions. Several calculated diversity indices show variable trends with increasing water depth, with at most only slight increases with depth. The bryozoans in this southern Caribbean reef assemblage do not show the well-defined depth zonation of corals. However, the recognition of deep- and shallow-water assemblages containing diagnostic species does show that cryptic reef-dwelling bryozoans have paleoecological utility as depth indicators in ancient reefs.
Hurricane effects on shallow-water cryptic reef molluscs, Fiji Islands
- David R. Kobluk, Mary A. Lysenko
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- Journal of Paleontology / Volume 67 / Issue 5 / September 1993
- Published online by Cambridge University Press:
- 20 May 2016, pp. 798-816
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An assemblage of 343 species of cryptic, shelled molluscs was identified in three large samples from shallow subtidal and intertidal shelter habitats under rubble and corals at Malololailai Fiji in 1983, 1984, and 1985. One species was a polyplacophoran, 273 were gastropods (38 families), and 69 were bivalves (21 families). Cryptic gastropods were more abundant than bivalves, but showed a reduction in abundance relative to bivalves from 1983 to 1985. The abundances of many cryptic molluscs show dramatic adjustments from 1983 to 1985, chiefly due to hurricanes in 1983 and 1985, showing a decrease in equitability with increased physical disturbance. The abundance and diversity of molluscan predators in the crypts means that predation in these habitats may be substantial.
The gastropod sample diversity showed the greatest change during the 1984 post-hurricane recovery period. The 1985 hurricanes affected the sample diversity by shifting the gastropod diversity closer to what it was after the 1983 hurricane. The bivalves underwent a similar shift in sample diversity, although larger numbers of individuals in proportionately more species survived the hurricanes.
The cryptic bivalves exploited space in new crypts, while maintaining their rate of increase in abundance in the recovery period after the 1983 hurricane and through the two hurricanes in 1985. The gastropods declined in abundance after the 1983 hurricane. They recovered after the 1985 hurricanes by doubling their abundance, showing that they could exploit new resources in crypts. This increase in the gastropod population was not proportional to the increase in available cryptic space. This may mean they were still recovering in August 1985, or they may have been unable to capture their portion of cryptic space in competition with other organisms during recovery.
The 1985 hurricanes did not have much effect on the overall molluscan diversity, a possible result of pruning by the 1983 hurricane of molluscs unable to survive storms. Because there was only a short interval between the hurricanes, many molluscs that survived the 1983 event were still in the population, so that the cryptic molluscs probably were better able to deal with the effects of the 1985 hurricanes than they would have been before the 1983 hurricane. The result was that the sample diversity after the 1983 hurricane increased during the recovery period but did not decline later even though the population was devastated by hurricanes in 1985. This lends support to intermediate disturbance models linking increasing or stable diversity with disturbances spaced at intervals allowing recovery.
Impact of two sequential Pacific hurricanes on sub-rubble cryptic corals: the possible role of cryptic organisms in maintenance of coral reef communities
- David R. Kobluk, Mary A. Lysenko
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- Journal of Paleontology / Volume 61 / Issue 4 / July 1987
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- 14 July 2015, pp. 663-675
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The hermatypic scleractinian cryptic coral biota living under mobile rubble in the reef flat and back reef zones of a Fijian fringing reef was surveyed in detail in August of 1984; only 138 days later the reef was struck by the first of two sequential hurricanes (57 days apart). The same sample areas were re-studied in August 1985, thereby providing the first detailed census of pre- and post-hurricane cryptic reef coral populations, and allowing an assessment of hurricane impact on these populations.
The 61 cryptic species (60 corals and Millepora) show 88 percent commonality with the intertidal and shallow subtidal reef surface coral population (68 species), and therefore are a good representation of the surface biota.
A major effect of the hurricanes was a reduction of almost 50 percent in the number of boulders sheltering cryptic coral. However, among boulders that retained coral through the storms, there was only a 5 percent reduction in the mean number of corals per boulder, signifying that damage to the surviving population was minor. The composition of the surviving cryptic coral population is essentially unchanged from its pre-hurricane state (there are differences in absolute abundances), and the relative importance of the species does not show marked change in most cases. Coral morphologies show little change in their absolute and relative percent abundances after the hurricanes. In contrast to what is normally seen in reef surface habitats, therefore, coral colony form did not appear to be an important determinant in survivability for those living under boulders; primary selection by the storms seems to have been on boulder form rather than cryptic coral form.
Cryptic sub-rubble coral populations may function as a preserve for elements of the pre-hurricane reef surface community. For example, delicately-branching forms that are commonly devastated in reef surface habitats during hurricanes may, in some cases, be preserved in great numbers under boulders or in other cryptic habitats. This provides a “recruitment pool” that can greatly accelerate their recovery and re-establishment on the post-hurricane reef surface, and dampen the potentially severe community dislocations arising from intense competition for space in “instantaneous” new reef substrate.