Table 2. --Mean depth, major benthic components (% cover), and surface area 



ratio on chain transects. 



St. Croix turfs). This means that the rates of organic matter production of 

 10.0, 14.7, and 13.9 g (dry)/m2/d on actual reef surfaces (rather than projected 

 area) are necessary to produce the rate of oxygen production we observed in the 

 water flowing over reefs. 



Tests of these theoretical rates of biomass production were supported in a 

 recent study in similar lagoon and back reef environments of Mayaguana in the 

 Bahamas (Adey and Goertemi 1 ler, in ms.). By harvesting algal turfs grown on 

 screens, actual biomass production was found to be 6-18 g (dry)/m2/d. A mean 

 rate of 12 g (dry)/m2/d, under a nutrient regime of 0.10-0.13 microgram-at N/1 

 (NO2 + NO3) (D'Elia, in prep.), was achieved. A similar and more recent study 

 at Grand Turk, Turk, and Caicos Islands (Peyton, et al . , in prep.) gave rates 

 of algal turf production of up to 31.8 g (dryJ/m^Td at nutrient concentrations 

 (as measured by NO2 + NO3 nitrogen) of less than 0.2 microgram-at N/1. Steneck 

 and Porter (in prep.) used a similar harvest technique for turfs growing on 

 slabs of coral substrata at a depth of 10 m and found a production rate of 6.0 

 g (dry)/m2/d. These harvest production rates are minimal since they do not 

 include losses to micro-herbi vores , abrasion, leaking of dissolved organics, or 

 the release of reproductive structures. Thus, the values we obtained using 

 upstream/downstream flow respirometry correspond well with measured rates of 

 biomass produced by this "functional group" of algae ( sensu Steneck and Wat 1 i ng, 

 1982) in the Caribbean. This also supports the pattern of high rates of 

 production (per unit biomass) for turf algae that have a high surface area to 

 volume ratio (Odum, et al . , 1958; Littler, et al . , 1983) and, perhaps equally 

 important, live in a strong wave surge environment. 



174 



