SITE SUMMARIES 149 MUTTON SNAPPER Description. The Mutton Snapper site is located on the landward side of a shelf edge spur and groove reef on the southwest shelf of St Croix in depths of 22-24 m. The reef was dominated by boulder star coral (primarily Orbicella franksi) until a mass coral die-off following the 2005 bleaching event. Mutton Snapper has been monitored since 2003. Outstanding Feature. The Mutton Snapper site was located in conjunction with the possible proximity of a mutton snapper (Lutjanus analis) spawning aggregation. It is seasonally closed to fishing. The site was devastated by the 2005 coral bleaching event, with an 87% drop in coral cover and a concomitant increase in algae. Threats. The Mutton Snapper site is threatened by fishing pressure as evidenced by the abundance of fishing line and fishing trap debris. This site is offshore and less likely threatened by land-based stressors. The clear waters and warm temperatures make this site vulnerable to long-term seawater warming. Figure 79. Mutton Snapper. (top) Location. (right) A representative photo of the reef taken in 2014. MUTTON SNAPPER 150 Figure 80. Mutton Snapper benthic temperature record at 23 m (left) and 39 m depth (right). Physical Characteristics. Current. Current records have not been taken at Mutton Snapper. There seems to be little wave-driven oscillatory flow. There are often strong unidirectional currents in a westward direction that penetrate to nearly the bottom. Temperature. Benthic temperatures at the Mutton Snapper site (23 m) show warming above the regional bleaching threshold during the 2010 bleaching event. This may be an overestimation of the heat stress since and empirical bleaching threshold has not yet been established for this site. However, coral health was assessed before the accumulation of heat stress in 2010, so a strong response may have occurred and not been detected. Month SITE SUMMARIES 151 Benthic Community. The Mutton Snapper site’s sessile epibenthic animal community is dominated the boulder star coral (Orbicella spp.), with sub-dominance of sponges. This site lost an extreme amount of coral cover (87.0%) in the 2005 coral bleaching event and has not regained any cover (-2.3%) as of 2011. Lobophora variegata, epilithic algae, and filamentous cyanobacteria dominate the algal community. Apparent is the rise in the abundance of macroalgae and filamentous cyanobacteria after 2005. Filamentous cyanobacteria reached extreme cover values (57.7%) in 2009. Current levels of herbivory no longer appear to be able to control algal abundance. Coral Health. Mutton Snapper bleached heavily in the 2005, with 100% of corals bleaching over 90% of the colony surface. Bleaching prevalence has remained high for most years since 2005, but at low colony extent, indicating continued impairment of corals. White disease has been at consistently high values through many years of monitoring. Old partial mortality increased after 2005, and then subsided as whole colonies were lost from the system. Impairment of this site is puzzling as stressors besides fishing appear to be low. Clear water and low genetic diversity of corals may increase susceptibility to environmental stress and white disease. Figure 81. Mutton Snapper (left) Relative composition of the sessile epibenthic animal community. (right) Relative composition of the algal community and unconsolidated sediment. MUTTON SNAPPER 152 Figure 82. Mutton Snapper benthic cover and coral health through time (mean ± SE). SITE SUMMARIES 153 Fish Community. The Mutton Snapper site is an offshore, shelf edge site with a fairly diverse and rich fish community. Fish biomass is generally low on the site; however, in 2014 surveys biomass was much higher than in earlier years. Mutton Snapper is reportedly in an area that mutton snapper spawn; however, mutton snapper have been very rare in surveys conducted at the site over the past 5 years. The Mutton Snapper site is very highly dominated in biomass by the black durgeon, a phytoplankton feeder, and numerically dominated by the creole wrasse, a zooplankton feeder. Stoplight parrotfish and doctorfish generally contribute the most biomass to the benthic herbivore group. Many parrotfish species can be found on the Mutton Snapper reef, however sub-adult and juveniles are by far the majority encountered. The invertivore group is also diverse, indicative of the variety of resources available on the reef. Piscivores are not common on Mutton Snapper and in general the biomass of this group was made up of primarily jacks and barracuda. Piscivorous serranids and lutjanids are usually limited to the graysby and mahogany snapper. Red lionfish are observed regularly on Mutton Snapper, probably because the reef is offshore and does not receive the diving and hunting pressure of nearshore sites. MUTTON SNAPPER 154 Figure 83. The Mutton Snapper fish community by absolute and relative biomass. Herbivores stoplight parrotfish doctorfish princess parrotfish striped parrotfish redband parrotfish ocean surgeonfish blue tang redfin parrotfish queen parrotfish Beaugregory orangespotted filefish threespot damsel greenblotch parrotfish cocoa damsel yellowtail damsel dusky damsel Fish Biomass (g) 0 1000 2000 3000 4000 5000 Invertivores blackbar soldierfish French grunt yellowhead wrasse red hind striped grunt fairy basselet butter hamlet Spanish hogfish squirrelfish white grunt highhat dusky squirrelfish clown wrasse harlequin bass longsnout butterflyfish Fish Biomass (g) 0 1000 2000 3000 4000 5000 6000 7000 Plankivores black durgon blue chromis yellowtail snapper bicolor damsel creole wrasse brown chromis sargassum triggerfish Fish Biomass (g) 0 2000 4000 6000 8000 10000 12000 14000 16000 Piscivores bar jack great barracuda graysby mahogany snapper glasseye snapper red lionfish Fish Biomass (g) 0 200 400 600 800 1000 1200 1400 SITE SUMMARIES 155 SALT RIVER WEST Description. Salt River West lies just atop the Salt River Canyon west wall in a depth of 9 m. The reef is a flat colonized hardbottom/coral community atop ancient carbonates. Salt River West has been monitored since 2001. Outstanding Feature. Salt River West is a popular tourist dive site with a unique sharp drop to the wall environment. This area has been under scientific investigation since the 1970s, beginning with the installation of the Hydrolab undersea habitat run by NOAA. Threats. Salt River West is exposed to the outflow from the Salt River Canyon and resuspension of sediment from the Salt River eastern flats. The site is now within in the Salt River National Historic Park and Ecological Preserve. This protection will hopefully increase the fish populations within the reserve in the coming decades. Figure 84. Salt River. (top) Location. (right) A representative photo of the reef with TCRMP researcher recording coral health data (Oct. 1, 2015). SALT RIVER WEST 156 Figure 85. Salt River West surface-benthic temperature record 5m depths. Data provided by the NOAA ICON monitoring network. Physical Characteristics. Current. Currents have not been directly measured by the TCRMP. Due to the northern exposure and shallow depth, Salt River West experiences wave-driven oscillatory flow, which can be strong. Unidirectional benthic currents are typically weak to moderate (<15cm s-1). Temperature. The temperature at Salt River West can be very warm and in 2005 surpassed the bleaching threshold (29.5°C) for approximately 2.5 months between August and October. Month SITE SUMMARIES 157 Benthic Community. The Salt River West epibenthic sessile animal community has a diverse hard coral community of small massive head corals and large proportions of sponges and gorgonians. The site lost an imperceptible amount of coral cover in the 2005 coral bleaching event (-13.6%) and had regained nearly half of that cover by 2011 (37.1%). The algal community shows extreme dominance by epilithic algae and low abundance of macroalgae and filamentous cyanobacteria. However, filamentous cyanobacteria have increased slightly since 2005. Coral Health. Corals were severely bleached during the 2005 coral bleaching event, with over 90% of corals bleached over 80% of the colony surface. Corals were assessed just prior to the 2010 bleaching event in August, but were showing increased prevalence of low colony extent bleaching by then. Diseases are typically low, with the outstanding case of dark spots disease, which attains some of the highest values seen in TCRMP sites. Of note, is the fact that dark spots disease actually decreased following severe bleaching and recovery in 2005 and 2006. Old partial mortality increased rapidly after the 2005 bleaching and then subsided somewhat by 2011. Recent partial mortality can be high and is primarily caused by fish biting, such as from parrotfish. However, extent is quite low (data not shown). Figure 86. Salt River West (left) Relative composition of the sessile epibenthic animal community. (right) Relative composition of the algal community and unconsolidated sediment. SALT RIVER WEST 158 Figure 87. Salt River West benthic cover and coral health through time (mean ± SE). SITE SUMMARIES 159 Fish Community. Fish biomass is relatively low on the Salt River West site. More diversity and some larger fishes can be seen close to the edge of the site, near the Salt River wall; however, the top of the reef has little structure for larger fishes, with low lying coral heads, gorgonians, and sponges. Wrasses and damselfishes are both numerous and diverse; the most dominant species on the site is the bluehead wrasse followed closely by the bicolor damselfish. Black durgeon, an opportunistic planktivore that feeds on zooplankton, phytoplankton and algae, dominates the Salt River West site in biomass, followed by the stoplight parrotfish, ocean surgeonfish, and very numerous creole wrasse. Piscivores are nearly non-existent, and include primarily graysby. Occasional red lionfish are seen on a Salt River West. Yellowfin snapper are the only lutjanids regularly encountered on the site, and these are observed only near the shelf edge. SALT RIVER WEST 160 Figure 88. The Salt River West fish community by absolute and relative biomass. Herbivores stoplight parrotfish ocean surgeonfish redband parrotfish princess parrotfish blue tang striped parrotfish redtail parrotfish doctorfish yellowtail damsel queen parrotfish orangespotted filefish dusky damsel Fish Biomass (g) 0 1000 2000 3000 4000 5000 6000 7000 Invertivores French grunt squirrelfish yellowhead wrasse slippery dick sand tilefish red hind smallmouth grunt harlequin bass spotted goatfish bluestriped grunt Spanish hogfish yellowtail hamlet Fish Biomass (g) 0 500 1000 1500 2000 2500 Plankivores black durgon creole wrasse blue chromis sunshinefish bicolor damsel brown chromis chalk bass Fish Biomass (g) 0 2000 4000 6000 8000 10000 12000 14000 16000 Piscivores trumpetfish graysby Fish Biomass (g) 0 50 100 150 200 250 SITE SUMMARIES 161 SALT RIVER DEEP Description. The Salt River Deep site is located on the steep canyon wall just below the Salt River West monitoring site. The reef consists of vertical buttresses surrounded by extensive sand deposits. The reef is largely formed of plating coral at these deep, mesophotic depths. The initial site was deployed in 2009 with two transects at 30 m depth and 4 transects at 40 m. Due to low coral cover at 40 m transects were moved to 30m in 2010. Outstanding Feature. Salt River Deep is a heavily visited recreational dive site. The site has been under scientific investigation since the 1970’s. The underwater HYDROLAB habitat was maintained near the site from 1977 to 1985 and the Aquarius habitat from 1986 to 1989. Threats. Salt River Deep is threatened by land-based sources of pollution due to its proximity to the Salt River Canyon outflow. The site may also be susceptible to warming temperatures. Figure 89. Salt River Deep. (top) Location. (right) A representative photo of the reef with TCRMP team (Oct. 1, 2015). SALT RIVER DEEP 162 Figure 90. Salt River Deep benthic temperature at 30 m depth (left) and 40 m depth (right). Physical Characteristics. Current. Salt River deep currents have not been measured directly by the TCRMP. Only very weak oscillatory and unidirectional currents have been experienced at the site. Temperature. Temperatures on the wall have been measured at two depth levels at 30 m and 40 m. Both sites have temperatures that are much cooler than the shallow site. The 40 m site experiences even greater cooling and experiences more diel variability (not shown) and day-to-day variability due to the influence of internal waves. Despite some interaction with the thermocline, cooling is not as great as at the mesophotic reefs at similar depths on the southern Puerto Rican Shelf. J F M A M J J A S O N D 24 25 26 27 28 29 30 31 2007 2008 2010 2011 Temperature ( oC) Month J F M A M J J A S O N D 24 25 26 27 28 29 30 31 2009 2010 2011 Temperature ( oC) Month SITE SUMMARIES 163 Benthic Community. Hard coral community of the Salt River Deep monitoring site is dominated by plating lettuce corals (Agaricia spp.); however, sponges, gorgonians, and black corals dominate the overall sessile epibenthic animal community. The site was not monitored during the 2005 bleaching event, but as with the Cane Bay Deep site, severe bleaching was observed down to depths of 40m. The algal community is dominated by epilithic algae and unidentified diminutive macroalgae. The site is notable for the high composition of sediment, which cascades from the upper reef between spurs and buttresses. Coral Health. Low extent coral bleaching is typically in moderate to high prevalence at the Salt River Deep site. Interaction data (not shown) indicates that sediment and Lobophora variegata overgrowth are responsible for much of the bleaching. Diseases have not been observed. Old partial mortality is high on corals, which may be a reflection of the 2005 bleaching event and cumulative impacts from interaction with sediment and algae. Figure 91. Salt River Deep (left) Relative composition of the sessile epibenthic animal community. (right) Relative composition of the algal community and unconsolidated sediment. SALT RIVER DEEP 164 Figure 92. Salt River Deep benthic cover and coral health through time (mean ± SE). SITE SUMMARIES 165 Fish Community. The relatively high turbidity and high composition of sand and silt bottom, as a consequence of river discharge, influences the fish community of Salt River Deep. The mesophotic reef wall site is characterized by a primarily invertivore fish community, leading in both biomass and species richness. Invertivores are dominated numerically by the functionally planktivorous blue chromis and creole wrasse. The benthic feeding yellow goatfish dominates the invertivore group by biomass, swimming in small schools along the sandy wall. Mahogany snapper and graysby are common piscivores. Sub-adult princess and redband parrotfish are the prominent herbivores. Characteristic deep water fishes observed commonly on Salt Water Deep include the sunshinefish, bantum bass, fairy basslet, and longsnout butterflyfish. As on the Cane Bay Deep site, occasional cubera snapper (Lutjanus cyanopterus), mutton snapper (L. analis), or southern stingrays (Dasyatis americana) are observed during roving dives on the wall, and commonly one or two small, curious Caribbean reef sharks (Carcharhinus perezi) are present. SALT RIVER DEEP 166 Figure 93. The Salt River Deep fish community by absolute and relative biomass. Herbivores redband parrotfish queen parrotfish ocean surgeonfish princess parrotfish redtail parrotfish striped parrotfish doctorfish threespot damsel midnight parrotfish stoplight parrotfish dusky damsel Fish Biomass (g) 0 500 1000 1500 2000 2500 Invertivores yellow goatfish fairy basselet black margate yellowhead wrasse Spanish hogfish French grunt spotted goatfish tomtate longsnout butterflyfish yellowtail hamlet bluestriped grunt white grunt smallmouth grunt butter hamlet Fish Biomass (g) 0 2000 4000 6000 8000 10000 12000 14000 16000 Plankivores yellowtail snapper creole wrasse black durgon blue chromis bicolor damsel sunshinefish tobaccofish chalk bass brown chromis Fish Biomass(g) 0 1000 2000 3000 4000 5000 Piscivores mahogany snapper graysby bar jack schoolmaster trumpetfish Fish Biomass (g) 0 200 400 600 800 1000 1200 1400 1600 1800 2000 SITE SUMMARIES 167 SPRAT HOLE Description. The Sprat Hole site is a nearshore/shelf-edge fringing reef in depths of 7 – 10 m. The site is a rolling boulder star coral (Orbicella annularis) reef. The slope to the west drops off to an attractive mixed coral community with abundant fish where it meets sand at about 25 m. Sprat Hole has been monitored since 2001. Outstanding Feature. Sprat Hole is a heavily visited reef for snorkel and dive tours. It supports a very diverse fish community. Threats. The Sprat Hole reef is vulnerable to land based sources of pollution if there is increased development of the watershed. Low wave action and light currents favor settling of small particles of terrestrial sediment that injure corals. The site is also frequently fished and there is derelict fishing gear in abundance. Recreational overuse may also be a threat. Figure 94. Sprat Hole. (top) Location. (right) A representative photo of the reef. SPRAT HOLE 168 Figure 95. Sprat Hole benthic temperature (7 m depth). Physical Characteristics. Current. Currents have not been measured at Sprat Hole. Oscillatory currents are typically weak on the western lee of St. Croix. Unidirectional currents during monitoring have always been weak (<10cm s-1). Temperature. Sprat Hole temperature has not been monitored over many years due to loss of probes. This is likely due to the high exposure to recreational and commercial fishing divers. Since 2013 temperature probes of the National Coral Reef Monitoring Program have been co-located at this site. In general Sprat Hole appears to be a warm site. Month SITE SUMMARIES 169 Benthic Community. Sprat Hole is a fringing Orbicella annularis dominated reef, with a good diversity of other coral species. There was a 62.3% decline in coral cover due to the 2005 coral bleaching event, with a regain of 11.9% of cover by 2011. Epilithic algae dominate the algal community, with smaller amounts of a diverse group of macroalgae, including Dictyota spp. and Halimeda spp. There has been variable, but increasing cover of filamentous cyanobacteria since 2005. Coral Health. The coral community at Sprat Hole was heavily affected during the 2005 coral bleaching event, with a high prevalence of bleaching at a very high extent. Bleaching prevalence has tended to be higher since the event. Disease prevalence can be quite high, particularly for white disease. Dark spots disease has also been in high prevalence in certain years. Old partial mortality was high on colonies from 2005 to 2011, and low when recorded in 2002. In this case, old partial mortality is a very common feature of O. annularis and it is likely that low values are due to observer bias and a different method for estimating partial mortality. Recent partial mortality is consistently very high at Sprat Hole, due in part to the high abundance of territorial damselfish (Stegastes spp.) forming algal lawns on O. annularis. Figure 96. Sprat Hole (left) Relative composition of the sessile epibenthic animal community. (right) Relative composition of the algal community and unconsolidated sediment. SPRAT HOLE 170 Figure 97. Sprat Hole benthic cover and coral health through time (mean ± SE). SITE SUMMARIES 171 Fish Community. Sprat Hole exhibits a fairly typical fish community structure for a nearshore coral reef ecosystem receiving some amount of terrestrial runoff from the watershed. Fish biomass is moderate, and the site is dominated numerically by the creole wrasse and blue chromis, planktivorous invertivores. Benthic herbivores are common and include small parrotfish and all three Caribbean acanthurid species. Invertivores are diverse and include both planktivores and benthic feeders; mostly small fish in small numbers. Mutton snapper have been recorded on the sight sporadically and a juvenile tiger grouper was spotted in 2013 and yellowfin grouper was seen in 2014. Numerically and by biomass the graysby dominate the piscivore group in. Lionfish have been observed on the Sprat Hole site every year since 2012. SPRAT HOLE 172 Figure 98. The Sprat Hole fish community by absolute and relative biomass. Herbivores stoplight parrotfish striped parrotfish threespot damsel redband parrotfish blue tang ocean surgeonfish princess parrotfish dusky damsel doctorfish queen parrotfish redfin parrotfish cocoa damsel greenblotch parrotfish Beaugregory Fish Biomass (g) 0 2000 4000 6000 8000 Invertivores mutton snapper yellowhead wrasse Spanish hogfish French grunt blackbar soldierfish red hind yellow goatfish squirrelfish clown wrasse slippery dick Caesar grunt spotted drum yellowtail hamlet yellowcheek wrasse striped grunt fairy basselet longsnout butterflyfish harlequin bass Fish Biomass (g) 0 500 1000 1500 2000 2500 3000 3500 Plankivores creole wrasse blue chromis brown chromis bicolor damsel yellowtail snapper black durgon Fish Biomass (g) 0 2000 4000 6000 8000 Piscivores graysby redspotted hawkfish spotted moray red lionfish spotted scorpionfish bar jack mahogany snapper schoolmaster nurseshark trumpetfish black hamlet Fish Biomass (g) 0 1000 2000 3000 4000 5000