Contributors | Affiliation | Role |
---|---|---|
Silbiger, Nyssa | California State University Northridge (CSUN) | Principal Investigator |
Adam, Tom C. | University of California-Santa Barbara (UCSB) | Scientist |
Burkepile, Deron | University of California-Santa Barbara (UCSB) | Scientist |
Putnam, Hollie | University of Rhode Island (URI) | Scientist |
Vega Thurber, Rebecca | Oregon State University (OSU) | Scientist |
Becker, Danielle M. | California State University Northridge (CSUN) | Student |
York, Amber D. | Woods Hole Oceanographic Institution (WHOI BCO-DMO) | BCO-DMO Data Manager |
See the "Related Datasets" section or the project page for other data collected as part of this study.
See the Project Page for more data collected as part of the project.
Our study was conducted following 15 months of nutrient enrichment during October 2019 at the control and nutrient-enriched sites on the north shore fore reef habitat in Mo'orea. We collected fragments of Pocillopora meandrina at each site based on morphological characteristics. However, due to recent analyses on the complexity of Pocillopora spp. identification, morphological characteristics are unreliable for species identification. Therefore, the coral fragments will be referred to as Pocillopora spp. for the remainder of the manuscript. Thirty-two Pocillopora spp. colonies showing no signs of bleaching were haphazardly collected in a block design with four fragments collected from each of four treatment or control blocks from depths of ~ 13 m. The treatment coral fragments were collected within < 0.5 m the nutrient diffusers for the nutrient-enriched treatment (n = 16) and ~ 20 m away from the diffusers for the control (n = 16) on October 15, 2019. Pocillopora spp. fragments were removed with hammer and chisel via SCUBA, placed in clean ziplock bags full of seawater, and returned to the boat.
The coral fragments for physiological assays were transported to the UCB Gump Station in a seawater filled cooler and immediately placed in flow-through seawater tables. Using a stainless steel diagonal cutter, fragments of each sample colony were cut into five replicate dimensions (7.8 cm × 7.8 cm) of multi-branch fragments, which were measured with calipers . Two fragments were used for light and dark respirometry trials, and two fragments were used for endosymbiont and coral response variables, including chlorophyll a content, endosymbiont densities, endosymbiont % nitrogen (N) content, endosymbiont N cell−1, tissue biomass, and coral tissue % N content.
The two fragments delegated for endosymbiont and coral response variables (one for % tissue N and one for the remaining parameters) were immediately frozen at −20 °C until processing. The two fragments designated for photosynthesis and respiration trials were affixed to pre-labeled acrylic coral plugs (Industry, CA, USA) using hot glue around the base of the coral skeleton while the fragment was submerged. After coral fragments were affixed, they were placed into one of two flow-through holding tanks (either control or nutrient-enriched) with filtered (pore size ~ 100 µm) seawater to recover from the fragmentation process for 7–12 days. The coral plugs were placed in individual holes on an acrylic sheet with an O-ring placed around the bottom of the plug for stabilization. The acrylic bases had 4 small 15-cm tall PVC pipes on the four corners of the base to keep the corals from being in contact with the bottom of the tank. Holding tank conditions were designed to mimic temperature and light regimes found at the collection sites.
Tissue removal
An Iwata Eclipse HP-BCS airbrush (Portland, OR, USA) filled with filtered seawater (0.2 μm) was used to remove coral tissue from the frozen coral skeleton. The resulting coral tissue slurries (n = 32 total) were individually homogenized for 15 s at 3,000 rpm with an electric handheld homogenizer (BT Lab Systems Saint Louis, MO, USA). Aliquots were taken from the tissue homogenate for each endosymbiont (chlorophyll a content, endosymbiont densities, % N content (% dry weight), and N content cell−1) and coral response variable (tissue biomass and % N content (% dry weight)) and frozen at −20 °C until further processing. Coral skeletons were dried at 60 °C for 4 h in a drying oven (Fisher Scientific Isotemp Oven, Waltham, MA, USA). After the skeletons were dry, the surface area was measured by dipping the skeletons in a 65 °C Minerva Paraffin Wax bath (Monroe, GA, USA) for 2 s, before removal and then rotating them quickly in the air (10 revolutions over 2 s). The coral skeletons were cooled at room temperature prior to being weighed. Surface area was calculated against a standard curve of mass change of wax dipped dowels against geometrically calculated surface area, with an R2 > 0.9 for the relationship.
Algal endosymbiont densities
Replicate cell counts (n = 6–8) were conducted for aliquoted (1 mL) coral tissue slurry samples, using an Improved Neubauer Haemocytometer (Marienfeld Superior, Lauda-Königshofen, Germany) to quantify algal endosymbiont densities. The endosymbiont cell densities were then normalized to coral surface area (cells cm−2).
Chlorophyll a content
Duplicate 3 mL samples from the tissue slurries were centrifuged (3,450 rpm × 3 min) (Fisher Scientific accuSpin™ 3R, Waltham, MA, USA) to isolate the algal pellet. 100% acetone was added to the algal pellet and placed in a freezer at −20 °C for 36 h in the dark. The supernatant of the extracted samples was measured spectrophotometrically (λ = 630, 663, and 750 nm) (Shimadzu UV-2450, Kyoto, Kyoto Prefecture, Japan), and concentrations of chlorophyll a were calculated using equations specified for dinoflagellates from Jeffrey and Humphrey (1975), after accounting for an acetone blank. The chlorophyll concentrations were then normalized to surface area (μg cm−2) and to endosymbiont cells (pg cell−1).
Tissue biomass
Triplicate 1 mL aliquots from each coral tissue slurry (n = 32) were pipetted into pre-burned aluminum pans (450 °C for 5 h) and then placed in a drying oven (Fisher Scientific Isotemp Oven, Waltham, MA, USA) at 60 °C for > 24 h until they reached a constant weight. Once the samples had reached a constant weight, they were placed in a muffle furnace (Fisher Scientific Isotemp Muffle Furnace, Waltham, MA, USA) at 450 °C for 4–6 h to determine ash-free dry weight. The total biomass of the aliquoted tissue slurry was the difference between the dried (60 °C) and burned (4–6 h at 450 °C) masses and the tissue biomass was expressed as mg cm−2.
Coral and endosymbiont tissue nitrogen content
To calculate coral tissue and endosymbiont N content, the skeletal carbonates were first separated from the host tissue and endosymbionts using a 20 μm nylon net filter (Wildco®, Yulee, FL, USA) and the remaining host tissue and endosymbiont cells were separated by centrifugation (3,450 rpm × 3 min.) (Fisher Scientific accuSpin™ 3R, Waltham, MA, USA) with 3–4 seawater rinses. To ensure separation efficiency between the coral tissue and endosymbionts, microscopic inspections were conducted on the supernatant and the endosymbiont pellets using a Leica Binocular Microscope (DM500, Feasterville, PA, USA) between each seawater rinse and centrifugation. If animal constituents, like nematocysts or spirocysts, were observed in the endosymbiont pellets, the sample was repeatedly resuspended and centrifuged until the final endosymbiont pellet had been properly washed and animal constituents were no longer observed. The same resuspension and centrifuge steps were taken if any endosymbiont cells were observed in the supernatant. Tissues were filtered onto weighed pre-combusted 25 mm GF/F filters (Whatman ®, Maidstone, UK) (450 °C, 4 h), dried overnight (80 °C), weighed, and placed in microcentrifuge tubes. Due to the vacuum filtration method, we note that host tissue samples may underestimate the total C and N content, since soluble material and particulate matter less than 0.7 μm would be lost in the process. CHN content for the coral host’s tissue and algal endosymbionts were analyzed at the UCSB MSI Analytical Lab using the same methods described above. Algal endosymbiont % N content and coral % N content were calculated by normalizing the N (mg) to the weight of the tissue on the filter (mg) and multiplying by 100. The N per algal endosymbiont cell (pg N cell−1) was also calculated.
Organism Life Science Identifiers (LSIDs):
Pocillopora meandrina, urn:lsid:marinespecies.org:taxname:206964
Pocillopora spp., urn:lsid:marinespecies.org:taxname:206938
All data and code are available at https://github.com/daniellembecker/Chronic_low_nutrient_enrichment_benefits_coral_thermal_performance_fore_reef_habitat (Release: v1.0.0 archival copy doi: 10.5281/ZENODO.5013255).
* Table within submitted file "coral_physiology.csv" was imported into the BCO-DMO data system for this dataset. Values "NA" imported as missing data values. Table will appear as Data File: 960140_v1_coral-bulk-physiology.csv (along with other download format options).
Missing Data Identifiers:
* In the BCO-DMO data system missing data identifiers are displayed according to the format of data you access. For example, in csv files it will be blank (null) values. In Matlab .mat files it will be NaN values. When viewing data online at BCO-DMO, the missing value will be shown as blank (null) values.
* Column names adjusted to conform to BCO-DMO naming conventions designed to support broad re-use by a variety of research tools and scripting languages. [Only numbers, letters, and underscores. Can not start with a number]
* Date converted to ISO 8601 format
* Organism names in this dataset were matched to Life Science Identifiers (LSIDs) using the World Register of Marine Species (WoRMS) on 2025-05-06.
Parameter | Description | Units |
fragment_ID | Unique Fragment ID | unitless |
chlA_ugcm2 | Chlorophyll concentration | micrograms per square centimeter (ug/cm2) |
SA_cm2 | Surface area of coral fragment | square centimeter (cm2) |
zoox_per_cm2 | Symbiont count ( x 10^6) per cm2 | counts x 10^6 per square centimeter (counts x 10^6 /cm2) |
treatment | treatment (enriched = nutrient encriched treatment; control = control) | unitless |
AFDW_mg_cm2 | organic biomass of coral tissue (Ash-Free Dry Weight) | milligrams per square centimeter (mg per cm2) |
Host_N_percent | Host tissue percent N | percent (%) |
Symbiont_N_percent | Symbiont percent N | percent (%) |
Symbiont_pgN_cell | Nitrogen concentration per cell for symbionts | picograms per cell (pg/cell) |
Date | Collection Date | unitless |
Location | Collection Location, Moorea forereef, north shore | unitless |
Dataset-specific Instrument Name | Iwata Eclipse HP-BCS airbrush (Portland, OR, USA) |
Generic Instrument Name | Airbrush |
Dataset-specific Description | An Iwata Eclipse HP-BCS airbrush (Portland, OR, USA) filled with filtered seawater (0.2 μm) was used to remove coral tissue from the frozen coral skeleton. |
Generic Instrument Description | Device for spraying liquid by means of compressed air. |
Dataset-specific Instrument Name | drying oven (Fisher Scientific Isotemp Oven, Waltham, MA, USA) |
Generic Instrument Name | Drying Oven |
Dataset-specific Description | Coral skeletons were dried at 60 °C for 4 h in a drying oven (Fisher Scientific Isotemp Oven, Waltham, MA, USA). |
Generic Instrument Description | a heated chamber for drying |
Dataset-specific Instrument Name | Improved Neubauer Haemocytometer (Marienfeld Superior, Lauda-Königshofen, Germany) |
Generic Instrument Name | Hemocytometer |
Dataset-specific Description | Improved Neubauer Haemocytometer (Marienfeld Superior, Lauda-Königshofen, Germany) paired with a a Leica Binocular Microscope (DM500, Feasterville, PA, USA) were used to quantify algal endosymbiont densities. |
Generic Instrument Description | A hemocytometer is a small glass chamber, resembling a thick microscope slide, used for determining the number of cells per unit volume of a suspension. Originally used for performing blood cell counts, a hemocytometer can be used to count a variety of cell types in the laboratory. Also spelled as "haemocytometer". Description from:
http://hlsweb.dmu.ac.uk/ahs/elearning/RITA/Haem1/Haem1.html. |
Dataset-specific Instrument Name | Leica Binocular Microscope (DM500, Feasterville, PA, USA) |
Generic Instrument Name | Microscope - Optical |
Dataset-specific Description | Improved Neubauer Haemocytometer (Marienfeld Superior, Lauda-Königshofen, Germany) paired with a a Leica Binocular Microscope (DM500, Feasterville, PA, USA) were used to quantify algal endosymbiont densities. |
Generic Instrument Description | Instruments that generate enlarged images of samples using the phenomena of reflection and absorption of visible light. Includes conventional and inverted instruments. Also called a "light microscope". |
Dataset-specific Instrument Name | Shimadzu UV-2450 (Kyoto, Kyoto Prefecture, Japan) |
Generic Instrument Name | UV Spectrophotometer-Shimadzu |
Dataset-specific Description | Chlorophyll was measured on a Shimadzu UV-2450 (Kyoto, Kyoto Prefecture, Japan). |
Generic Instrument Description | The Shimadzu UV Spectrophotometer is manufactured by Shimadzu Scientific Instruments (ssi.shimadzu.com). Shimadzu manufacturers several models of spectrophotometer; refer to dataset for make/model information. |
NSF Award Abstract:
Submarine groundwater discharge (SGD) is the flow of water from land through the coastal seafloor into the nearby ocean. Approximately 13,000 cubic kilometers of groundwater is discharged into coastal environments every year, yet the effects of this fresh and often nutrient rich SGD are still poorly understood for coral reefs. This SGD input is driven by changes in precipitation, human land use, sea-level rise, tidal amplitude, and groundwater usage, many of which are rapidly changing with climate and human impacts. This project improves our understanding of SGD effects on coral reefs to better predict how both natural and human-induced changes will affect coastal ecosystem functioning in the future. Working in one of the most comprehensively studied coral reef ecosystems in the Pacific (Mo'orea, French Polynesia, home of the Mo'orea Coral Reef Ecosystem LTER); this project tests the influence of SGD on individual, community, and ecosystem-scale coral reef processes. Using mensurative studies, caging experiments, and a synthetic model, the investigators: 1) characterize SGD gradients and relate it to high resolution coral reef cover data, 2) determine how individual to ecosystem processes are influenced by SGD, and 3) develop a synthetic model to show how changes in SGD fluxes will alter reef ecosystem functioning. As SGD is a common feature on nearshore coral reefs worldwide, the results of this study have global implications for understanding the performance of coral reefs, which are essential economic, cultural, and scientific resources. This project is structured to provide training across multiple career levels, linking 13 undergraduate students, 2 graduate students, 2 senior personnel, 1 postdoctoral researcher, 1 female beginning lead investigator, and 2 senior co-investigators, with a focus on encouraging participation from underrepresented groups (e.g., through the Alaska Native and Native Hawaiian, Asian American and Native American Pacific Islander, and Hispanic-Serving Institutions of California State University Northridge, the University of Hawaiʻi at Mānoa, and California State University Long Beach). The investigators work with local K-12 students and teachers in Mo'orea and collaborate with an artist-in-residence to communicate science to the broader public through interactive and immersive art experiences in Mo'orea, Miami, and Los Angeles.
SGD is a natural and understudied feature of many nearshore coral reef ecosystems, which can contribute substantial changes to marine biogeochemistry, with impacts for coastal organisms such as reef-building corals, macroalgae, and bioeroders. SGD may play a key role in coral reef ecosystem functioning because it alters key physicochemical parameters (e.g., temperature, salinity, and nutrient and carbonate chemistry) that substantially affect both biotic and abiotic processes on coral reefs. This project (i) characterizes the spatial extent and biogeochemical signal of SGD in Mo'orea, French Polynesia, (ii) identifies how SGD influences microbial processes, benthic organism growth rates and physiology, species interactions between corals, macroalgae, and herbivores, and net ecosystem calcification and production rates, and (iii) quantitatively assesses how changes in SGD fluxes will alter reef biogeochemistry and ecosystem functioning through an integrative modelling effort. Specifically, the hydrogeological, biogeochemical, and ecological data collected in this study are synthesized in a Bayesian structural equation model. This project characterizes and quantifies how SGD directly and indirectly affects ecosystem functioning via changes in biogeochemistry and altered individual to ecosystem responses, thereby providing a better capacity to track and predict alterations in reef ecosystem function.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
Funding Source | Award |
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NSF Division of Ocean Sciences (NSF OCE) |