Marine & Environmental Sciences Faculty Reports

Document Type

Article

Publication Date

10-30-1997

Abstract

Monitoring of benthic macroinvertebrate assemblages in the vicinity of Port Everglades Southport began in September 1988 in anticipation of dredging of the Southport Turning Notch and concomitant mitigation of mangrove habitats at adjacent areas of John U. Lloyd State Recreation Area. Twice-yearly surveys were carried out from September 1988 to January 1991 by Sheldon Dobkin (Florida Atlantic University), and subsequently, from August 1991 to January 1997, under the supervision of Charles G. Messing and Richard E. Dodge (Nova Southeastern University Oceanographic Center). From 1990 onward, surveyed sites consisted of 11 Ponar grab stations, 11 mangrove crab census stations, and three intertidal hand collection stations.

Ponar grab collections: Surveys from August 1991 to January 1997 enumerated 100,524 organisms identified to 370 species. Overall organism abundance peaked in January 1993 through January 1994, declined through 1995 and recovered in 1996. Overall species richness followed a similar trend, with the largest number of species recorded in the final survey. Several taxa of invertebrates, including polychaetes, oligochaetes, mollusks, sipunculans and peracarid crustaceans, are consistently important faunal components at several stations, and may represent useful indicators of future environmental perturbations. The fauna at station 17 in Whisky Creek appears to be unique and worthy of careful preservation. Possible faunal changes here may be the result of taxonomic difficulties. The most distinct trend observed was a seasonal variation in numbers of certain polychaetes and crustaceans at a few stations. Because the previous contractor overlooked or did not identify a substantial percentage of the fauna, pre- and postdredging comparisons are extremely limited. However, with the possible exception of unidentified sabellid polychaetes found in numbers adjacent to the dredging site during and before dredging, but rarely afterward, dredging of the Turning Basin appears to have had little effect on infaunal macroinvertebrate assemblages in the Intracoastal Waterway.

Crab collections: Censusing of mangrove crabs at the seven stations north of the Turning Basin on the west side of the Intracoastal Waterway reveals two important features: a strong seasonal trend, with larger populations recorded in summertime surveys (except during the summer of dredging, 1989), and a steep decline in populations of most species after 1992, including the disappearance of the formerly most abundant species, Sesarma curacaoense. This species also disappeared from station 15 on the east side of the ICWW. Crab numbers also declined at east side station 10. Finally, the fiddler crab, Uca rapax, has become the dominant species and has increased in numbers over the last several surveys at east side station 16.

Hand collections: Station 9 has maintained a typical rocky intertidal fauna throughout the project. However, barnacles have declined while a vermetid gastropod, tentatively identified as Petaloconchus varians, has increased substantially in numbers. Several red mangrove trees along the fringe margin died during 1995, increasing the exposure of the site and perhaps accounting for the appearance of encrusting sponges and colonial tunicates. Stations 13 and 17 have remained relatively unchanged, although attached bivalves have increased in numbers at the former site since 1993. The gastropod, Batillaria minima, and the springtail insect, Anurida maritima, dominate both stations.

Comments

"Prepared for: Port Everglades Authority" From caption.

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