15 JUNE 1999
K.A. Hovel, S.G. Morgan-1999
Journal of Experimental Marine Biology and Ecology, 237(1): 107-125 (from Current Contents)
Abstract:
Estuarine crab larvae are often hatched into shallow salt marshes and may remain near the water's surface while dispersing from shorelines. Residence in surface waters or entrapment in shallow backwaters of marshes may expose larvae to damaging ultraviolet radiation-B (UVBR, 280-320 nm). To determine the effects of UVBR exposure on larval survival, larvae of three species of salt marsh crabs, Uca pugnax (Smith, 1870), Sesarma reticulatum (Say, 1817), and Dyspanopeus sayi (Smith, 1869), were reared for 4 days in UVBR-transparent and UVBR-opaque containers that were suspended 10 and 25 cm below the sea surface in a shallow salt marsh located on Long Island, New York, USA. UVBR, UV-A radiation (UVAR, 320-400 nm) and photosynthetically active radiation (PAR, 400-700 nm) were measured from the surface to the bottom of the water column during the course of five replicate trials. UVBR, UVAR and PAR were all rapidly attenuated in the turbid salt marsh. Nevertheless, UVBR decreased larval survival of all three species. Survival of Sesarma reticulatum larvae decreased as UVBR exposure increased during the course of the experiment. Survival of Uca pugnax larvae initially declined but stabilized thereafter. Survival of Dyspanopeus sayi larvae did not decline during the first day of the experiment but it decreased each day thereafter. Therefore, UVBR may quickly kill newly hatched larvae that become trapped in the marsh or remain within 1 m of the water's surface. However, larvae in Flax Pond were released during nocturnal ebb tides, and 97.7% of newly hatched larvae were flushed from the marsh before daybreak. Thereafter, larvae may avoid the top 1 m of the water column during the daytime (U. pugnax and D. sayi) or may reside at depth throughout the day (S. reticulatum). The two surface oriented species also may be protected from UVBR by photorepair mechanisms or mycosporine-like amino acids (MAAs). Though larvae remaining high in the water column may be exposed to sublethal doses of UVBR, larvae of these three species may not be killed directly by short-term exposure to UVBR while dispersing from temperate shorelines.
(Coll William & Mary, Sch Marine Sci, POB 1346, Gloucester Point, VA 23062, USA, e-mail: khovel@vims.edu)