Algal cover from herbivore exclusion and nutrient enrichment experiments conducted in the Florida Keys National Marine Sanctuary during 2009-2012

Website: https://www.bco-dmo.org/dataset/639509
Data Type: experimental
Version: 1
Version Date: 2016-03-02

Project
» Cascading interactions of herbivore loss and nutrient enrichment on coral reef macroalgae, corals, and microbial dynamics (HERBVRE)
ContributorsAffiliationRole
Burkepile, DeronFlorida International University (FIU)Principal Investigator
Vega Thurber, RebeccaFlorida International University (FIU)Co-Principal Investigator
Copley, NancyWoods Hole Oceanographic Institution (WHOI BCO-DMO)BCO-DMO Data Manager

Abstract
This dataset contains summary percent cover data for algal species and other encrusting invertebrates found in the study plots in the Florida Keys National Marine Sanctuary during 2009-2012.


Coverage

Spatial Extent: Lat:24.9943 Lon:-80.4065
Temporal Extent: 2009-06 - 2012-08

Methods & Sampling

Natural history of the study site:
This experiment was conducted in the area of Pickles Reef (24.99430, -80.40650), located east of Key Largo, Florida in the United States. The Florida Keys reef tract consists of a large bank reef system located approximately 8 km offshore of the Florida Keys, USA, and paralleling the island chain. Our study reef is a 5-6 m deep spur and groove reef system within this reef tract. The reefs of the Florida Keys have robust herbivorous fish populations and are relatively oligotrophic. Coral cover on most reefs in the Florida Keys, including our site, is 5-10%, while macroalgal cover averages ~15%, but ranges from 0-70% depending on location and season. Parrotfishes (Scaridae) and surgeonfishes (Acanthuridae) are the dominant herbivores on these reefs as fishing for them was banned in 1981. The other important herbivore on Caribbean reefs, the urchin Diadema antillarum, remains at low densities across the Florida Keys following the mass mortality event in 1982-3

Exclosure and nutrient enrichment experimental design details
In order to simulate the effects of overfishing, nutrient loading, or the combination of these stressors, we conducted a three-year field experiment. Four pairs of 9m2 plots were established. One member of each of these pairs was enriched with nitrogen and phosphorous, while the other remained at ambient nutrient levels. These plots were >10 m from each other in all cases. Each 9 m2 plot was delineated into nine 1 m2 subplots with metal nails driven into the reef at the corners and center of each plot. The locations of the plots were selected such that initial variation in rugosity and algal cover within each subplot was minimal. Within each plot, two randomly-selected subplots were enclosed with herbivore exclosures, while two other random subplots were selected as exclosure controls. Exclosure controls were fitted with open-topped exclosures. These controls allowed access by herbivorous fishes but acted as controls for other potential artifacts of the cages.

All exclosures were made of plastic-coated wire mesh with 2.5 cm diameter holes. This diameter mesh generally excludes most fishes >10 cm total length. Smaller or juvenile herbivorous fishes are able to enter the exclosures, but these smaller herbivores generally contribute little to overall grazing rates on reefs and have minimal impacts on the algal communities. Additionally, access by smaller herbivores reflects patterns seen under intensive fishing, in which larger fish species are preferentially harvested while leaving smaller size classes of fish. We scrubbed both exclosures and exclosure controls every 4-6 weeks to remove fouling organisms.

Nutrient pollution was simulated using slow-release fertilizer diffusers applied to each nutrient enrichment plot. Each diffuser was a 15 cm diameter PVC tube, perforated with six 1.5 cm holes. The open ends of the PVC tube were wrapped in fine plastic mesh to keep fertilizer pellets inside, but allow diffusion of soluble nutrients. 175 g of Osmocote® (19-6-12, N-P-K) slow-release fertilizer was loaded into each diffuser. PVC enrichment tubes were attached to each metal nail within the 9m2 enrichment plots for a total of 25 enrichment tubes per enrichment plot. Nutrients were replaced every 30-40 days to ensure continued delivery of N and P. Previous studies have shown Osmocote delivery using similar methods to be an effective way of enriching water column nutrients in benthic systems.

Quantification of Benthic Cover
At least once every season (e.g. Spring, Summer, Fall, Winter at 12-14 week intervals), we visually quantified benthic cover within four, 50 cm X 50 cm quadrats in each of the 1 m2 treatment areas. These quadrats were divided into 49 points, and benthic organisms under each point were identified to species or genus. Algae that are challenging to identify taxonomically under field conditions (e.g. crustose coralline algae, filamentous algae) were classified into algal functional groups (e.g. 52). Filamentous algae were classified into short algal turf (< 0.5 cm in height) or algal turf (> 0.5 cm in height) given that taller, thicker algal turf can often be deleterious to coral health and growth.

Benthic cover was quantified in June 2009 one week before treatments were initiated to provide a baseline from which to assess changes in algal abundance and community structure. No significant differences among treatments in algal abundance could be detected at the beginning of the experiment, as expected given random assignment of subplots to treatment conditions. Further, during the summer of each year (2009-2012) when algal cover was often at its highest, we also surveyed open areas of reef (areas that did not have three-sided exclosure controls) with the 9 m2 plots to assess whether the exclosure controls had any effect on algal abundance or community composition. We did not detect any differences in algal abundance or community composition between the open unmanipulated areas and exclosure controls.


Data Processing Description

BCO-DMO Processing:
- added conventional header with dataset name, PI name, version date, reference information
- renamed parameters to BCO-DMO standard
- added site, lab, lat, lon columns
- replaced blank cells with nd
- replaced spaces with underscores; removed ()


[ table of contents | back to top ]

Data Files

File
cover.csv
(Comma Separated Values (.csv), 56.04 KB)
MD5:e64ac1f5d88c725df1a2c565fd4910f9
Primary data file for dataset ID 639509

[ table of contents | back to top ]

Related Publications

Zaneveld, J. R., Burkepile, D. E., Shantz, A. A., Pritchard, C. E., McMinds, R., Payet, J. P., … Thurber, R. V. (2016). Overfishing and nutrient pollution interact with temperature to disrupt coral reefs down to microbial scales. Nature Communications, 7(1). doi:10.1038/ncomms11833
Results

[ table of contents | back to top ]

Related Datasets

IsRelatedTo
Burkepile, D., Vega Thurber, R. (2021) Algal species ID from herbivore exclusion and nutrient enrichment experiments conducted in the Florida Keys National Marine Sanctuary during 2009-2012 (HERBVRE project). Biological and Chemical Oceanography Data Management Office (BCO-DMO). (Version 1) Version Date 2016-12-19 doi:10.26008/1912/bco-dmo.639480.1 [view at BCO-DMO]
Burkepile, D., Vega Thurber, R. (2021) Water column nutrients for ambient nutrient conditions from Pickles Reef in Upper Florida Keys, 2009-2012 (HERBVRE project). Biological and Chemical Oceanography Data Management Office (BCO-DMO). (Version 1) Version Date 2016-03-01 doi:10.26008/1912/bco-dmo.639563.1 [view at BCO-DMO]

[ table of contents | back to top ]

Parameters

ParameterDescriptionUnits
sitestudy site unitless
latlatitude; north is positive decimal degrees
lonlongitude; east is positive decimal degrees
month_yearmonth and year of survey Mon-YYYY
season_yearseason and year of survey Season_YYYY
yearyear YYYY
seasonseason unitless
blockblock number: a pair of two 9 meter square plot unitless
plotplot number unitless
nutrient_tmtcontrol = ambient nutrients; enriched = mimicked nutrient pollution by addition of fertilizer unitless
herbivore_tmtuncaged = open to herbivores (Exclosure Control); caged = excluded herbivores (Exclosure) unitless
repreplicate number unitless
treatment_idtreatment identification: block; nutrient tmt; herbivore tmt; replicate unitless
CCAcrustose coralline algae coverage percent
short_tufcoverage by short turf less than 0.5 cm percent
tall_turfcoverage by tall turf greater than 0.5 cm percent
Total_Dictyotatotal Dictyota coverage percent
Total_Sargassumtotal Sargassum coverage percent
Total_macroalgaetotal macroalgae coverage percent
Total_cyanobacteriatotal cyanobacteria coverage percent
Total_upright_algal_covertotal upright algal coverage percent

[ table of contents | back to top ]

Deployments

Burkepile_FL_Keys

Website
Platform
Florida Keys National Marine Sanctuary
Start Date
2009-06-01
End Date
2012-08-31
Description
Herbivore effects on reef algae


[ table of contents | back to top ]

Project Information

Cascading interactions of herbivore loss and nutrient enrichment on coral reef macroalgae, corals, and microbial dynamics (HERBVRE)

Coverage: Key Largo, Florida Keys, USA; N 24.99430, W 080.40650


Description from NSF award abstract:
Coral reefs in the Caribbean Sea are undergoing unprecedented declines in coral cover due in large part to climate change, pollution, and reductions in fish biodiversity and abundance. Macroalgae have become abundant on reefs, probably due to decreases in herbivory (e.g., through overfishing) and increases in anthropogenic inputs of nutrients. The spread of macroalgae has negative feedbacks on reef recovery because algae are often superior competitors and suppress growth of both adult and juvenile corals. A majority of reef studies to date have focused on how stressors affect macroorganisms, while relatively few have investigated how these stressors and the resultant algal-dominated states affect microorganisms. Yet, coral reef-associated microbes play significant roles in coral reef ecosystems through biogeochemical cycling and disease. Since microbes are important mutualists of corals as well as potential pathogens, it is important to understand the mechanisms that control their taxonomic and functional diversity.

The goal of this proposal is to quantify how alterations of top-down (removal of herbivorous fish) and bottom-up (inorganic nutrient addition) forces alter macrobial as well as microbial dynamics on coral reefs in order to understand the mechanisms that reinforce coral-depauperate reef systems. This work asks two main questions:

Q1. How do nutrient enrichment and herbivore removal interact to affect benthic algal abundance, coral-algal interactions, and coral survivorship and growth?

Q2. How do nutrient enrichment and herbivore removal affect bacterial abundance, taxonomic diversity, and functional diversity on and within corals?

The proposed research will directly and empirically address many of the current hypotheses about how bottom-up and top-down forces alter reef dynamics. The PIs will investigate: (1) the impact of multiple stressors over several years; (2) impacts on multiple levels of biological organization (from fishes to algae to microbes); and (3) the mechanisms underlying changes in algal-coral microbe interactions. Significantly, the approach will provide the statistical power necessary to distinguish between seasonal- and stress-induced changes in macro- and microbial diversity.

Resulting Publication:
Zaneveld, J.R., D.E. Burkepile, A.A. Shantz, C. Pritchard, R. McMinds, J. Payet, R. Welsh, A.M.S. Correa, N.P. Lemoine, S. Rosales, C.E. Fuchs, and R. Vega Thurber (2016) Overfishing, nutrient pollution, and temperature interact to disrupt coral reefs down to microbial scales. Nature Communications 7:11833 doi:10.1038/ncomms11833.
Access to data via Supplementary Information.



[ table of contents | back to top ]

Funding

Funding SourceAward
NSF Division of Ocean Sciences (NSF OCE)

[ table of contents | back to top ]