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This protocol outlines a method of quantitatively measuring the degree of bleaching of a coral colony nondestructively in the field using image analysis. Previous studies have shown that mean intensity grey (MIG), also known as percent whiteness, is highly correlated with chlorophyll a and Symbiodiniaceae density (Chow et al. 2016, Amid et al. 2018), and therefore can be used to quantify the bleaching intensity of a coral colony. Color analysis can be done using digital photographs of live coral colonies either in situ (e.g., Maguire et al. 2003) or exsitu in the lab (Amid et al. 2018; this protocol). Photographs must be taken prior to any preservation or processing of tissue, such as freezing, use of preservatives or fixatives, airbrushing etc., to ensure no alteration of the original coral color occurs. In this protocol, corals are photographed in front of a white reference standard and the resulting color images are subsequently converted to 8-bit greyscale and analyzed. There are two steps to this protocol: 1) Photographing live coral fragments 2) Image analysis of mean grey value
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Airbrushed coral sample preparation for organic stable carbon and nitrogen isotope analysis
This method for separating coral tissues from algal endosymbiont (Symbiodiniaceae) for stable isotope analysis is modified from previously published methods (Hughes et al. 2010). There are three parts to preparing coral samples for stable carbon and nitrogen isotope analysis: 1) airbrush to remove coral tissue and algal cells from skeleton and store at -80 °C until ready to separate, 2) separate the coral tissue from the algal cells through centrifugation and filtering, and 3) dry and pack separated tissues into tin capsules for analysis in a stable isotope ratio mass spectrometer. This method was modified from Hughes et al. (2010) by James Price with the assistance of Alex Smith and Kerri Dobson and with the guidance of Andréa Grottoli at The Ohio State University. dx.doi.org/10.17504/protocols.io.bgi7juhn
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- Award ID(s):
- 1838667
- PAR ID:
- 10214888
- Date Published:
- Journal Name:
- Protocolsio
- ISSN:
- 2473-1838
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Coral morphology is influenced by genetics, the environment, or the interaction of both, and thus is highly variable. This protocol outlines a non-destructive and relatively simple method for measuring Scleractinian coral subcorallite skeletal structures (such as the septa length, theca thickness, and corallite diameter, etc.) using digital images produced as a result of digital microscopy or from scanning electron microscopy. This method uses X and Y coordinates of points placed onto photomicrographs to automatically calculate the length and/or diameter of a variety of sub-corallite skeletal structures in the Scleractinian coral Porites lobata. However, this protocol can be easily adapted for other coral species - the only difference may be the specific skeletal structures that are measured (for example, not all coral species have a pronounced columella or pali, or even circular corallites). This protocol is adapted from the methods described in Forsman et al. (2015) & Tisthammer et al. (2018). There are 4 steps to this protocol: 1) Removal of Organic Tissue from Coral Skeletons 2) Imaging of Coral Skeletons 3) Photomicrograph Image Analysis 4) Calculation of Corallite Microstructure Size dx.doi.org/10.17504/protocols.io.bx5bpq2nmore » « less
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Abstract Coral reefs are threatened by anthropogenic climate change, which causes ocean acidification and warming that can result in coral death and the loss of genetic diversity on reefs around the world. Global efforts to secure the genetics of threatened populations using cryopreservation and biobanking are underway but are limited to coral sperm and larvae, available only during brief annual spawning events. Methods to cryopreserve adult coral tissues to enable biobanking activities year‐round are urgently needed, but are challenging due to the presence of a calcium carbonate skeleton and algal symbionts within the tissues, and chill sensitivity. In this study, vitrification and laser nanowarming permitted successful recovery of adult coral tissues in a novel sample type, the single‐polyp microfragment. Fluorescence and confocal microscopy shows clearly defined green fluorescent protein auto‐fluorescence around the polyp mouth post‐warming, with an overall survival rate of 39.7 ± 7.4% at 24 h post‐warming and 23.3 ± 9.7% at 1 month, but relatively few algal symbionts are present in the tissues, indicating poor survival of these cells. These proof‐of‐concept results provide a basis for continued research and development of a field‐ready protocol for cryopreservation of adult coral tissues, which will be essential to prevent extinctions and support reef restoration.more » « less
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Abstract Corals obtain nutrition from the photosynthetic products of their algal endosymbionts and the ingestion of organic material and zooplankton from the water column. Here, we use stable carbon (δ13C) and nitrogen (δ15N) isotopes to assess the proportionate contribution of photoautotrophic and heterotrophic sources to seven Hawaiian coral species collected from six locations around the island of O‘ahu, Hawaiʻi. We analyzed the δ13C and δ15N of coral tissues and their algal endosymbionts, as well as that of dissolved inorganic matter, particulate organic matter, and zooplankton from each site. Estimates of heterotrophic contribution varied among coral species and sites. Bayesian mixing models revealed that heterotrophic sources (particulate organic material and zooplankton) contributed the most toPocillopora acutaandMontipora patulacoral tissues at 49.3% and 48.0%, respectively, and the least toPorites lobataat 28.7%, on average. Estimates of heterotrophic contribution based on the difference between δ13C of the host and algal endosymbiont (δ13Ch–e) and isotopic niche overlap often differed, while estimates based on δ15Nh–ewere slightly more aligned with the estimates produced using Bayesian mixing models. These findings suggest that the utility of each approach may vary with coral health status, regions, and coral species. Overall, we find that the mean heterotrophic contribution to Hawaiian coral tissues ranges from 20% to 50%, suggesting a variety of trophic strategies. However, these findings did not always match past direct measurements of heterotrophic feeding, indicating that heterotrophically acquired nutrition does not necessarily get incorporated into tissues but can be respired or exuded in mucus.more » « less
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Abstract All biology happens in space, and spatial structuring plays an important role in mediating biological processes at all scales from cells to ecosystems. However, the metabolomic structuring of the coral holobiont has yet to be fully explored. Here, we present a method to detect high-quality metabolomic data from individual coral polyps and apply this method to study the patterning of biochemicals across multiple spatial (~1 mm - ~100 m) and organizational scales (polyp to population). The data show a strong signature for individual coral colonies, a weaker signature of branches within colonies, and variation at the polyp level related to the polyps’ location along a branch. Mapping metabolites to either the coral or algal components of the holobiont reveals that polyp-level variation along the length of a branch was largely driven by molecules associated with the cnidarian host as opposed to the algal symbiont, predominantly putative sulfur-containing metabolites. This work yields insights on the spatial structuring of biochemicals in the coral holobiont, which is critical for design, analysis, and interpretation of studies on coral reef biochemistry.more » « less
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.17504/protocols.io.bgi7juhn
