DOCSLIB.ORG

Pulsed Delivery of Subthermocline Water to Conch Reef (Florida Keys) by Internal Tidal Bores Author(S): James J

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Pulsed Delivery of Subthermocline Water to Conch Reef (Florida Keys) by Internal Tidal Bores Author(S): James J Pulsed Delivery of Subthermocline Water to Conch Reef (Florida Keys) by Internal Tidal Bores Author(s): James J. Leichter, Stephen R. Wing, Steven L. Miller, Mark W. Denny Reviewed work(s): Source: Limnology and Oceanography, Vol. 41, No. 7 (Nov., 1996), pp. 1490-1501 Published by: American Society of Limnology and Oceanography Stable URL: http://www.jstor.org/stable/2838529 . Accessed: 29/03/2012 21:28 Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at . http://www.jstor.org/page/info/about/policies/terms.jsp JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. American Society of Limnology and Oceanography is collaborating with JSTOR to digitize, preserve and extend access to Limnology and Oceanography. http://www.jstor.org Limnol.Oceanogr., 41(7), 1996, 1490-1501 ? 1996, by the American Society of Limnologyand Oceanography,Inc. Pulseddelivery of subthermoclinewater to ConchReef (FloridaKeys) by internaltidal bores JamesJ. Leichter StanfordUniversity, Hopkins Marine Station,Pacific Grove, California93950 StephenR. Wing Wildlife,Fish and ConservationBiology, University of Californiaat Davis 95616 StevenL. Miller National Undersea Research Center,University of North Carolina at Wilmington28403 Mark W. Denny StanfordUniversity, Hopkins Marine Station Abstract Internaltidal boresgenerated by breakinginternal waves cause dramatic,high-frequency variation in temperature,salinity, water velocities, and concentrationof chlorophylla on ConchReef, Florida Keys. The arrivalof bores on thereef slope is linkedto a semidiurnalinternal tide and is markedby temperature drops of up to 5.4?Cand salinityincreases of up to 0.60ooin 1-20 min.These changesare accompaniedby the suddenonset of upslopeflow 1-15 m above thebottom with speeds of 10-30 cm s-'. Cool, high-salinity wateris transportedfrom below the thermocline seaward of the reef and is residenton thereef slope for up to 4 h beforeit mixeswith surface waters and recedesdownslope. Compared with ambient surface water, thisdeep watercan containsignificantly elevated concentrations of dissolvednitrate. Physical variability producedby this mechanism increases significantly with depth on thereef slope. Analysis of 3-yr temperature recordsindicates the arrival of internal bores is a consistentfeature at thissite from May through November, withpeak activity in July-September.Pulsed delivery of subthermocline water appears to significantlyaffect thetemperature, nutrient, and particleflux regimes on thiscoral reef. The sources, dynamics,and consequences of physical cause coral reefsflourish in environmentswith limited variabilityin coral reefecosystems have interestedbiol- seasonal variabilityand low nutrientconcentrations, in- ogistfor at least 150 years.For example, Darwin's (1962 termittentdelivery of deep, nutrient-richwater may sig- [ 1842]) observationthat reefs grow fastest near shelfedges, nificantlyaffect temperature and nutrientregimes (Wo- Goreau's (1959) descriptionof the effect of wave exposure lanskiand Pickard 1983; Wolanski 1994). Similarly,tran- on coral species distributions,Connell's (1978) formu- sientmovement of plankton-richwater onto a reefcould lation ofthe relationship between disturbance and species be an importantsource of suspendedparticles and larvae. diversity,and manyrecent studies of physical disturbance This studyexamines internaltidal bores as a mechanism in reef ecosystems(see Hughes 1993) all recognize the of persistent,high-frequency physical variabilityon the fundamentalimportance of temporal and spatial envi- slope of Conch Reef (Florida Keys). ronmentalvariability. Single factorsrarely explain the Internalbores are generatedby breakinginternal waves. patternsand dynamicsof coral reefs.However, the study In any stablystratified body of water,where densityin- of environmentalvariability provides an underlyingcon- creases either continuouslyor discretelywith depth, a text for understandingthese complex ecosystems. Be- varietyof mechanisms can produceinternal waves (Baines 1986). Tidal forcingof a stratifiedwater column over the margins of a continentalshelf can generate packets of Acknowledgments internalwaves that tend to propagate inshore along the We thankC. Cooper,S. Genovese,D. Hanisak,T. Hopkins, thermocline(Baines 1986; Holloway 1991). As these L. Morgan,M. Samples,G. Shellenbarger,J. Styren,G. Villa, waves run into shallow water over gradually sloping D. Ward,K. Watkins,J. Witting,and thestaff of the National shelves,they steepen, and increasingshear at the density UnderseaResearch Center for assistance in thefield. J. Bascom, discontinuityleads to instabilityand breaking.The re- R. Bourgeirie,M. Connolly,and W. Wilmotof the National Ocean Servicesprovided instrumentation. We thankR. Jones sultingturbulent bores of subthermoclinewater -internal fornutrient analysis. Two anonymousreviewers provided crit- surf-continue to travel inshore, mixing with ambient icismof the manuscript. surfacewater (Wallace and Wilkinson 1988; Holloway This researchwas supportedby the NationalOceanic and 1991; Pineda 1994). In wave tanks, breaking internal AtmosphericAdministration through National Undersea Re- waves cause vertical mixing (Wallace and Wilkinson searchProgram grants 9306 and 9422. 1988), and it has been suggested that internal waves 1490 Internalbores on ConchReef 1491 breakingon continentalshelves may cause transientup- wellingin coastal marineenvironments (e.g., Cooper 1947; Wolanskiand Pickard 1983; Sandstromand Elliott1984). The existenceof internalwaves was well documented by the 1950s (Ewing 1950), and theirpresence in all ocean basins has been recognized since the 1970s. Only since the 1970s, however, has their potential ecological im- portance been studied in detail. Haury et al. (1979) re- ported high frequencyinternal waves in Massachusetts Bay and proposed that they could produce significant redistributionof plankton. Shea and Broenkow (1982) detected large amplitude internaltides and a potential effecton thenutrient regime of MontereyBay, California. Surface slicks travelingwith internalwaves have been implicatedin the shorewardtransport of neustonic larvae along the coast of southernCalifornia (Shanks 1983) and New Zealand (Kingsfordand Choat 1986). Pineda (1991, Fig. 1. Map of southernFlorida with schematic represen- 1994) showed shoreward transportof cool, subsurface tationof the studysite at ConchReef (inset) seaward of Key water in turbulentbores, followed by onshore transport Largo.An arrayof instruments deployed across the reef on five of surfacewarm frontsand larvae in southernCalifornia. 7-15-d cruises consisted of vertical strings of thermistors based Semidiurnalvertical oscillations of the thermoclinehave at 35 and 21 m,electromagnetic current and conductivity-tem- been described as a mechanism of nutrientdelivery to perature-depthmeters at 21 and3 5 m,moored acoustic Doppler southernCalifornia kelp forests(Zimmerman and Kre- currentprofiler at 35 m (November1993 only), and individual mer 1984). Frederiksenet al. (1992) suggestedsuspended thermistorsat 3-mdepth increments from 30 to 12 m. particledelivery by internalwaves could explain patchy distributionsof a deep-waterscleractinian coral in the that run fromthe reefcrest at a depth of 12 to -30 m, northeasternAtlantic. Witman et al. (1993) documented where the formationsbreak up into a series of isolated transportof warm, phytoplankton-richwater to dense patches surroundedby coral sand. A mix of primarily aggregationsof sessile suspensionfeeders on shallow pin- mounding and plating corals as well as benthic algae, nacles in theGulf of Maine. Andrewsand Gentien(1982), sponges,and softcorals covers most available space on Wolanski and Pickard (1983), and Wolanski (1994) have the reef. At -35 m, the reef ends on a gentlysloping, pointed to tidal oscillations of the thermoclinein the continuoussand plain thatextends, uninterrupted, for 8- Coral Sea as a potentialsource of nutrientsfor the outer 10 km to the deep channel of the Florida Strait.The reef shelf of the Great Barrier Reef, and Novozhilov et al. lies withinthe Florida Keys National Marine Sanctuary, (1992) reportedevidence of tidal upwellingnear reefsin and all measurementswere made at the site of the Na- the SeychellesIslands. Internalwaves and bores seem to tional Undersea Research CenterAquarius Habitat. The be a widespreadphenomenon (Pineda 1995), but reports site was accessed from small boats and measurements fromcoral reefsare few,and other studies to date have were made with both Nitrox (36%0 2) and saturation not documented the dramatic and repeated forcingof diving. subthermoclinewater onto a coral reefthat we observed at Conch Reef. Long-term measurements-Long-term temperature Our observationsof largetemperature and salinityfluc- data were collectedby continuousdeployment of instru- tuations accompanied by rapid increases in flow speeds mentson the reefslope at 7, 21, and 3 5 m fromlate 1991 on a tidal cycle led to a workinghypothesis that internal to 1994. Ryan Tempmentorswere moored 1 m above waves weredriving the shorewardtransport of water from the bottom and sampled at 20-min intervalsfor deploy- belowthe thermocline. Physical conditions associated with ments lastingup to 3 months.
Load more

Recommended publications
  • Benthic Communities at Two Remote Pacific Coral Reefs: Effects of Reef
    Benthic communities at two remote Pacific coral reefs: eVects of reef habitat, depth, and wave energy gradients on spatial patterns Gareth J. Williams1,7 , Jennifer E. Smith1,7 , Eric J. Conklin2, Jamison M. Gove3,4 , Enric Sala5,6 and Stuart A. Sandin1 1 Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, USA 2 The Nature Conservancy, Honolulu, Hawaii, USA 3 Coral Reef Ecosystem Division, Pacific Islands Fisheries Science Center, USA 4 Joint Institute for Marine and Atmospheric Research, University of Hawaii at Manoa, Honolulu, Hawaii, USA 5 National Geographic Society, Washington, DC, USA 6 Centre d’Estudis Avanc¸ats de Blanes (CSIC), Blanes, Spain 7 These authors contributed equally to this work. ABSTRACT Kingman Reef and Palmyra Atoll in the central Pacific are among the most re- mote coral reefs on the planet. Here we describe spatial patterns in their benthic communities across reef habitats and depths, and consider these in the context of oceanographic gradients. Benthic communities at both locations were dominated by calcifying organisms (54–86% cover), namely hard corals (20–74%) and crustose coralline algae (CCA) (10–36%). While turf algae were relatively common at both locations (8–22%), larger fleshy macroalgae were virtually absent at Kingman (<1%) and rare at Palmyra (0.7–9.3%). Hard coral cover was higher, but with low diversity, in more sheltered habitats such as Palmyra’s backreef and Kingman’s patch reefs. Al- most exclusive dominance by slow-growing Porites on Kingman’s patch reefs provides indirect evidence of competitive exclusion, probably late in a successional sequence.
    [Show full text]
  • In Situ Tagging and Tracking of Coral Reef Fishes from the Aquarius Undersea Laboratory
    TECHNICAL NOTE In Situ Tagging and Tracking of Coral Reef Fishes from the Aquarius Undersea Laboratory AUTHORS ABSTRACT James Lindholm We surgically implanted coded-acoustic transmitters in a total of 46 coral reef fish Stellwagen Bank National Marine Sanctuary; during a saturation mission to the Aquarius Undersea Laboratory in August 2002. Current address: Pfleger Institute of Aquarius is located within the Conch Reef Research Only Area, a no-take marine re- Environmental Research serve in the northern Florida Keys National Marine Sanctuary. Over the course of 10 Sarah Fangman days, with daily bottom times of 7 hrs, saturation diving operations allowed us to col- Channel Islands National Marine Sanctuary lect, surgically tag, release, and subsequently track fishes entirely in situ. Fish were collected using baited traps deployed adjacent to the reef as well as nets manipulated Les Kaufman on the bottom by divers. Surgical implantation of acoustic transmitters was conducted Boston University Marine Program at a mobile surgical station that was moved to different sites across the reef. Each fish Steven Miller was revived from anesthetic and released as divers swam the fish about the reef. Short- National Undersea Research Center, term tracking of tagged fish was conducted by saturation divers, while long-term fish University of North Carolina at Wilmington movement was recorded by a series of acoustic receivers deployed on the seafloor. Though not designed as an explicit comparison with surface tagging operations, the benefits of working entirely in situ were apparent. INTRODUCTION he use of acoustic telemetry to track the movements of marine fishes is now a com- true with deepwater fishes that have air blad- fish with a damp towel.
    [Show full text]
  • Aquarius Fact Sheet
    Fact Sheet: 2019 Designer: Perry Submarine Builders (Florida) Construction: Victoria Machine Works (Texas); start: 1986 | complete: 1987 Estimated construction cost: $5.5M Operational Timeline: St. Croix Deployment: Deployment in Salt River Canyon, St. Croix: 1987 Owner: NOAA Operator: Farleigh Dickenson University Interim Period: Recovered: 1990 by the University of North Carolina Wilmington Refurbished: 1990-1993 at North Carolina State Ports, Wilmington, NC Owner: NOAA Operator: University of North Carolina Wilmington Florida Keys Deployment: Initial deployment on Conch Reef, Florida Keys: 1993 (baseplate deployed 1992) Recovered for refurbishment: 1996-1998 - Harbor Branch Oceanographic Institution, Ft. Pierce, FL Redeployment on Conch Reef, Florida Keys: 1998 – present Owner: NOAA: 1986-2014; Florida International University: 2014 – present Operator: FDU: 1987-1989; UNCW: 1990-2012; Florida International University: 2013 - present Aquarius Siting: Conch Reef, Florida Keys (Florida Keys National Marine Sanctuary): Distance From Islamorada shore base: 15.4 km (8.5 nm) Distance offshore: 9 km (5.4 nm) Hatch depth/storage depth: 14 m (46 fsw) 35 psi Depth of bottom directly below Aquarius: 18 m (60 fsw) (updated: 09.15.19) Habitat Specifications: Aquarius weight: 82-ton double-lock pressure vessel Baseplate weight: 120 tons Dimensions: 14-meters long by 3-meters in diameter (46 ft x 10 ft) Crew: 4 scientists and 2 technicians Amenities: kitchen facilities that include a microwave, instant hot water dispenser, refrigerator, sink, dining
    [Show full text]
  • Review on Hard Coral Recruitment (Cnidaria: Scleractinia) in Colombia
    Universitas Scientiarum, 2011, Vol. 16 N° 3: 200-218 Disponible en línea en: www.javeriana.edu.co/universitas_scientiarum 2011, Vol. 16 N° 3: 200-218 SICI: 2027-1352(201109/12)16:3<200:RHCRCSIC>2.0.TS;2-W Invited review Review on hard coral recruitment (Cnidaria: Scleractinia) in Colombia Alberto Acosta1, Luisa F. Dueñas2, Valeria Pizarro3 1 Unidad de Ecología y Sistemática, Departamento de Biología, Facultad de Ciencias, Pontificia Universidad Javeriana, Bogotá, D.C., Colombia. 2 Laboratorio de Biología Molecular Marina - BIOMMAR, Departamento de Ciencias Biológicas, Facultad de Ciencias, Universidad de los Andes, Bogotá, D.C., Colombia. 3 Programa de Biología Marina, Facultad de Ciencias Naturales, Universidad Jorge Tadeo Lozano. Santa Marta. Colombia. * [email protected] Recibido: 28-02-2011; Aceptado: 11-05-2011 Abstract Recruitment, defined and measured as the incorporation of new individuals (i.e. coral juveniles) into a population, is a fundamental process for ecologists, evolutionists and conservationists due to its direct effect on population structure and function. Because most coral populations are self-feeding, a breakdown in recruitment would lead to local extinction. Recruitment indirectly affects both renewal and maintenance of existing and future coral communities, coral reef biodiversity (bottom-up effect) and therefore coral reef resilience. This process has been used as an indirect measure of individual reproductive success (fitness) and is the final stage of larval dispersal leading to population connectivity. As a result, recruitment has been proposed as an indicator of coral-reef health in marine protected areas, as well as a central aspect of the decision-making process concerning management and conservation.
    [Show full text]
  • Status of Cuban Coral Reefs
    Bull Mar Sci. 94(2):229–247. 2018 research paper https://doi.org/10.5343/bms.2017.1035 Status of Cuban coral reefs 1 Centro de Investigaciones Patricia González-Díaz 1 * Marinas, Universidad de 2, 3 La Habana, Calle 16 No. 114, Gaspar González-Sansón Miramar, Playa, Havana 11300, Consuelo Aguilar Betancourt 2, 3 Cuba. Sergio Álvarez Fernández 1 2 Departamento de Estudios Orlando Perera Pérez 1 para el Desarrollo Sustentable 1 de la Zona Costera, Universidad Leslie Hernández Fernández de Guadalajara, Gómez Farías 82, Víctor Manuel Ferrer Rodríguez 1 San Patricio-Melaque, Cihuatlán, Yenisey Cabrales Caballero 1 Jalisco, CP 48980, Mexico. 1 3 Maickel Armenteros Canadian Rivers Institute, 100 1 Tucker Park Rd, Saint John, NB Elena de la Guardia Llanso E2L 4A6, Canada. * Corresponding author email: <[email protected]>. ABSTRACT.—Cuban coral reefs have been called the “crown jewels of the Caribbean Sea,” but there are few comparative data to validate this claim. Here, we provide an overview of Cuban coral reefs based on surveys carried out between 2010 and 2016 on seven of the main Cuban coral reef systems: Havana, Artemisa, Los Colorados, Punta Francés, Los Canarreos Archipelago, Península Ancón, and Jardines de la Reina. Ecological indicators were evaluated for each of these areas at the community level. Results suggest differences among benthic communities (corals, sponges, and gorgonians) that are most evident for reefs that develop near highly urbanized areas, such as Havana, than for those far from the coast and less accessible. Offshore reefs along the south-central coast at Jardines de la Reina and Península Ancón exhibited high coral density and diversity.
    [Show full text]
  • Assessing Long-Term Changes in the Beach Width of Reef Islands Based on Temporally Fragmented Remote Sensing Data
    Remote Sens. 2014, 6, 6961-6987; doi:10.3390/rs6086961 OPEN ACCESS remote sensing ISSN 2072-4292 www.mdpi.com/journal/remotesensing Article Assessing Long-Term Changes in the Beach Width of Reef Islands Based on Temporally Fragmented Remote Sensing Data Thomas Mann 1,* and Hildegard Westphal 1,2 1 Leibniz Center for Tropical Marine Ecology, Fahrenheitstrasse 6, D-28359 Bremen, Germany; E-Mail: [email protected] 2 Department of Geosciences, University of Bremen, D-28359 Bremen, Germany * Author to whom correspondence should be addressed; E-Mail: [email protected]; Tel.: +49-421-2380-0132; Fax: +49-421-2380-030. Received: 30 May 2014; in revised form: 7 July 2014 / Accepted: 18 July 2014 / Published: 25 July 2014 Abstract: Atoll islands are subject to a variety of processes that influence their geomorphological development. Analysis of historical shoreline changes using remotely sensed images has become an efficient approach to both quantify past changes and estimate future island response. However, the detection of long-term changes in beach width is challenging mainly for two reasons: first, data availability is limited for many remote Pacific islands. Second, beach environments are highly dynamic and strongly influenced by seasonal or episodic shoreline oscillations. Consequently, remote-sensing studies on beach morphodynamics of atoll islands deal with dynamic features covered by a low sampling frequency. Here we present a study of beach dynamics for nine islands on Takú Atoll, Papua New Guinea, over a seven-decade period. A considerable chronological gap between aerial photographs and satellite images was addressed by applying a new method that reweighted positions of the beach limit by identifying “outlier” shoreline positions.
    [Show full text]
  • Nature Parks Snorkeling Surfing Fishing
    Things to do in Florida Nature Parks Snorkeling Surfing Fishing Nature Parks Green Cay This nature center is the county’s newest nature canter that over- looks 100 acres of constructed wetland. Wakodahatchee Wetlands Is a park in Delray Beach with a three-quarter mile boardwalk that crosses between open water ponds and marches. Patch Reef Park & DeHoernle Park Parks in Boca Raton that have an abundant of sports and recreation facilities. Morikami Museum & Japanese Gardens The gardens at this Japanese cultural center in Delray Beach in- clude paradise garden, various styles of rock and Zen gardens, and a museum. Gumbo Limbo This Nature Center and Environmental Complex includes an indoor museum with fish tanks with fish, turtles, and other sea life. It is also known for rehabilitating and protecting sea turtles. *More information and website links are located on the last page. Snorkeling Blowing Rocks This is an environmental preserve on Jupiter Island in Hobe Sound. This peaceful, barrier island sanctuary is known for large-scale, native coastal habitat restoration. Lantana Beach Lantana is a coastal community in Palm Beach and 10 feet off shore there is a pretty good areas to snorkel. Red Reef Park A 67-acre oceanfront park in Boca Raton for swimming, snorkeling, and surf fishing that includes a nature center. Lauderdale-by-the-Sea Is known as “The Shore Diving Capital of South Florida”. There are two coral reef lines that are just a short swim from the beach. John Pennekamp Coral Reef State Park The first undersea park that encompasses about 70 natural square miles.
    [Show full text]
  • Coral Reef Algae
    Coral Reef Algae Peggy Fong and Valerie J. Paul Abstract Benthic macroalgae, or “seaweeds,” are key mem- 1 Importance of Coral Reef Algae bers of coral reef communities that provide vital ecological functions such as stabilization of reef structure, production Coral reefs are one of the most diverse and productive eco- of tropical sands, nutrient retention and recycling, primary systems on the planet, forming heterogeneous habitats that production, and trophic support. Macroalgae of an astonish- serve as important sources of primary production within ing range of diversity, abundance, and morphological form provide these equally diverse ecological functions. Marine tropical marine environments (Odum and Odum 1955; macroalgae are a functional rather than phylogenetic group Connell 1978). Coral reefs are located along the coastlines of comprised of members from two Kingdoms and at least over 100 countries and provide a variety of ecosystem goods four major Phyla. Structurally, coral reef macroalgae range and services. Reefs serve as a major food source for many from simple chains of prokaryotic cells to upright vine-like developing nations, provide barriers to high wave action that rockweeds with complex internal structures analogous to buffer coastlines and beaches from erosion, and supply an vascular plants. There is abundant evidence that the his- important revenue base for local economies through fishing torical state of coral reef algal communities was dominance and recreational activities (Odgen 1997). by encrusting and turf-forming macroalgae, yet over the Benthic algae are key members of coral reef communities last few decades upright and more fleshy macroalgae have (Fig. 1) that provide vital ecological functions such as stabili- proliferated across all areas and zones of reefs with increas- zation of reef structure, production of tropical sands, nutrient ing frequency and abundance.
    [Show full text]
  • The Economic, Social and Icon Value of the Great Barrier Reef Acknowledgement
    At what price? The economic, social and icon value of the Great Barrier Reef Acknowledgement Deloitte Access Economics acknowledges and thanks the Great Barrier Reef Foundation for commissioning the report with support from the National Australia Bank and the Great Barrier Reef Marine Park Authority. In particular, we would like to thank the report’s Steering Committee for their guidance: Andrew Fyffe Prof. Ove Hoegh-Guldberg Finance Officer Director of the Global Change Institute Great Barrier Reef Foundation and Professor of Marine Science The University of Queensland Anna Marsden Managing Director Prof. Robert Costanza Great Barrier Reef Foundation Professor and Chair in Public Policy Australian National University James Bentley Manager Natural Value, Corporate Responsibility Dr Russell Reichelt National Australia Bank Limited Chairman and Chief Executive Great Barrier Reef Marine Park Authority Keith Tuffley Director Stephen Fitzgerald Great Barrier Reef Foundation Director Great Barrier Reef Foundation Dr Margaret Gooch Manager, Social and Economic Sciences Stephen Roberts Great Barrier Reef Marine Park Authority Director Great Barrier Reef Foundation Thank you to Associate Professor Henrietta Marrie from the Office of Indigenous Engagement at CQUniversity Cairns for her significant contribution and assistance in articulating the Aboriginal and Torres Strait Islander value of the Great Barrier Reef. Thank you to Ipsos Public Affairs Australia for their assistance in conducting the primary research for this study. We would also like
    [Show full text]
  • Artificial Reef Observations from a Manned Submersible Off Southeast Florida
    BULLETIN OF MARINE SCIENCE, 44(2): 1041-1050, 1989 ARTIFICIAL REEF OBSERVATIONS FROM A MANNED SUBMERSIBLE OFF SOUTHEAST FLORIDA Eugene A, Shinn and Robert I. Wicklund ABSTRACT Examination of 16artificial reef structures with a two-person submersible in depths ranging from 30 to 120 m (100-400 ft) indicated that the highest numbers offish are found around reefs in water shallower .than 46 m (150 ft). Fewer fish, especially those with tropical coral reef affinities, below 46 m was probably caused by a thermocline, observed on all dives deeper than 43 m (140 ft). During 4 days in September 1987, temperatures from the surface down to approximately 43 m were 30° to 31°C (86°-88°F), whereas below 43 m the temperature dropped as low as 1O.6°C(51°F) at 120 m (390 ft). Algae and reef community encrusters (gorgonians, bryozoans, branching sponges, and corals), abundant on shallower structures, were absent below 46 m. Structures that penetrated above the thermocline, such as two upright oil "rigs" and a hopper barge, were also effective reefs. The open structure and high profile of the rigs enhance their use as artificial reefs by providing a range of well-aerated habitats. Any effect of substrate or post-deployment age on fish abundance could not be documented. Wood appeared to be a more effective fish-concentrating material but has a shorter useful life than does steeL The greatest diversity and numbers of fish were observed at the Miami sewer outfalL Numerous derelict ships and other material have been placed off southeast Florida for the purpose of enhancing fish stocks and sportsfishing.
    [Show full text]
  • Lasting Effects of Damage from a Cruise Ship Anchor on a Coral Reef in St
    BULLETIN OF MARINE SCIENCE, 69(2): 793–803, 2001 TEN YEARS AFTER THE CRIME: LASTING EFFECTS OF DAMAGE FROM A CRUISE SHIP ANCHOR ON A CORAL REEF IN ST. JOHN, U.S. VIRGIN ISLANDS Caroline S. Rogers and Virginia H. Garrison ABSTRACT In October 1988, a cruise ship dropped its anchor on a coral reef in Virgin Islands National Park, St. John, creating a distinct scar roughly 128 m long and 3 m wide from a depth of 22 m to a depth of 6 m. The anchor pulverized coral colonies and smashed part of the reef framework. In April 1991, nine permanent quadrats (1 m2) were established inside the scar over a depth range of 9 m to 12.5 m. At that time, average coral cover inside the scar was less than 1%. These quadrats were surveyed again in 1992, 1993, 1994, 1995 and 1998. Recruits of 19 coral species have been observed, with Agaricia agaricites and Porites spp. the most abundant. Quadrats surveyed outside the scar in June 1994 over the same depth range had a higher percent coral cover (mean = 7.4%, SD = 4.5) and greater average size (maximum length) of coral colonies than in quadrats inside the damaged area. Although coral recruits settle into the scar in high densities, live coral cover has not increased significantly in the last 10 yrs, reflecting poor survival and growth of newly settled corals. The relatively planar aspect of the scar may increase the vulner- ability of the recruits to abrasion and mortality from shifting sediments. Ten years after the anchor damage occurred, live coral cover in the still-visible scar (mean = 2.6%, SD = 2.7) remains well below the cover found in the adjacent, undamaged reef.
    [Show full text]
  • Upwelling As a Source of Nutrients for the Great Barrier Reef Ecosystems: a Solution to Darwin's Question?
    Vol. 8: 257-269, 1982 MARINE ECOLOGY - PROGRESS SERIES Published May 28 Mar. Ecol. Prog. Ser. / I Upwelling as a Source of Nutrients for the Great Barrier Reef Ecosystems: A Solution to Darwin's Question? John C. Andrews and Patrick Gentien Australian Institute of Marine Science, Townsville 4810, Queensland, Australia ABSTRACT: The Great Barrier Reef shelf ecosystem is examined for nutrient enrichment from within the seasonal thermocline of the adjacent Coral Sea using moored current and temperature recorders and chemical data from a year of hydrology cruises at 3 to 5 wk intervals. The East Australian Current is found to pulsate in strength over the continental slope with a period near 90 d and to pump cold, saline, nutrient rich water up the slope to the shelf break. The nutrients are then pumped inshore in a bottom Ekman layer forced by periodic reversals in the longshore wind component. The period of this cycle is 12 to 25 d in summer (30 d year round average) and the bottom surges have an alternating onshore- offshore speed up to 10 cm S-'. Upwelling intrusions tend to be confined near the bottom and phytoplankton development quickly takes place inshore of the shelf break. There are return surface flows which preserve the mass budget and carry silicate rich Lagoon water offshore while nitrogen rich shelf break water is carried onshore. Upwelling intrusions penetrate across the entire zone of reefs, but rarely into the Lagoon. Nutrition is del~veredout of the shelf thermocline to the living coral of reefs by localised upwelling induced by the reefs.
    [Show full text]