Restoring the three-dimensionality of hurricane-impacted coral reefs in Puerto Rico
Project funded by the National Fish and Wildlife Foundation
Backgound:
In September 2017, category five Hurricanes Irma (Sept. 6, 2017) and María (Sept. 20, 2017) devastated the island of Puerto Rico, including its coral reefs. The impacts of storm-generated waves extirpated or significantly reduced most of the populations of the reef building corals Acropora cervicornis, A. palmata and Orbicella annularis across the island’s northeastern coast. These corals contribute significantly to the structural complexity of Caribbean coral reefs. In their absence the three-dimensional structure of most impacted coral reefs has been largely flattened or severely compromised across multiple locations. Because the functioning, resilience, and ecosystems services of coral reefs depend on the structural complexity of the reef framework, there is an urgent need to re-establish the three-dimensionality of the impacted reefs. For instance, the structural complexity of coral reefs facilitates ecological processes such as predation, herbivory and nutrient cycling that in turn help coral and fish recruitment and promote recovery/resistance and restoration success. Furthermore, reef structural complexity is directly involved in wave energy dissipation protecting from the direct impact of waves not only adjacent coastal ecosystems (e.g., seagrass meadows and mangrove forests) but also coastal communities. Therefore, it is critical to incorporate a multi-method restoration approach to recover and boost reef structural complexity, which harnesses ecological processes that facilitate the recovery of habitat availability, functioning, resilience and services provided by coral reefs.
In September 2017, category five Hurricanes Irma (Sept. 6, 2017) and María (Sept. 20, 2017) devastated the island of Puerto Rico, including its coral reefs. The impacts of storm-generated waves extirpated or significantly reduced most of the populations of the reef building corals Acropora cervicornis, A. palmata and Orbicella annularis across the island’s northeastern coast. These corals contribute significantly to the structural complexity of Caribbean coral reefs. In their absence the three-dimensional structure of most impacted coral reefs has been largely flattened or severely compromised across multiple locations. Because the functioning, resilience, and ecosystems services of coral reefs depend on the structural complexity of the reef framework, there is an urgent need to re-establish the three-dimensionality of the impacted reefs. For instance, the structural complexity of coral reefs facilitates ecological processes such as predation, herbivory and nutrient cycling that in turn help coral and fish recruitment and promote recovery/resistance and restoration success. Furthermore, reef structural complexity is directly involved in wave energy dissipation protecting from the direct impact of waves not only adjacent coastal ecosystems (e.g., seagrass meadows and mangrove forests) but also coastal communities. Therefore, it is critical to incorporate a multi-method restoration approach to recover and boost reef structural complexity, which harnesses ecological processes that facilitate the recovery of habitat availability, functioning, resilience and services provided by coral reefs.
Goal: This project aims to restore the structural complexity of coral reefs that were flattened by the impacts of the hurricanes Irma and Maria in the Island Municipality of Culebra, Puerto Rico. We are employing an innovative multi-method restoration approach that combines the outplanting of artificial coral colonies (ACC) created with emerging 3D printing technology with multispecies outplants composed of morphologically complex branching (A. cervicornis and A. palmata) and massive corals (Orbicella spp.). This project is funded by the National Fish and Wildlife Foundation.
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We are specifically targeting reef whose restoration will improve coastal resilience in Culebra by:
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History of our project
Fieldwork 1. The project officially started
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On August 28th, a group of volunteers from the Capitulo Estudiantil Sociedad Ambiente Marino (CESAM) joined our team during the project's first day of fieldwork. The aim was to secure and reinforce our coral nursery units due to the possible impact of tropical storm Isaac. Coral are modular organisms that grow by replicating partially self-maintaining multicellular units known as polyps. This unique aspect of their biology allows corals to remain viable even when a portion of their total number of polyps in corals die or are detached. The potential of individual polyps to be established as independent colonies have provided the basis for many conservation strategies to increase local population abundance. For instance, coral gardening, one of the current and most common alternatives employed to propagate the acroporids corals species, consists of collecting individual branches from wild colonies and growing them in nursery units. See the picture below for an example of the current coral propagation unit we are currently using.
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Fieldwork 2 & 3: Establishment of coral propagation units
One of this project's goals is to increase the number of coral propagation units (coral nurseries). Several research studies have demonstrated that growing coral colonies in propagation units improve their demographic performance (i.e., growth and survival). Coral propagation units can, among other things, reduce competition-related stress. Many fragment-based aquaculture techniques (e.g., A-frames, hanging ropes, coral trees) have been developed to promote the recovery of coral reefs ecosystems. This human-assisted asexual propagation has been put into practice in at least 12 localities in the wider Caribbean.
Fieldwork 4: Characterization of reef substrate
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A preliminary site assessment was performed to characterize the reef conditions and the restoration suitability of sites within the area of interest in Punta Tampico and Punta Maguey. Around 50 waypoints at each site were randomly created at a minimum distance of 50 m apart and placed within an area of interest identified as a reef by the NOAA-NMFS 2015 Benthic Map. The assessment consisted of visually inspecting each waypoint's benthic conditions by recording the depth, presence of hard substrate, type of reef, the reef's level of complexity and coral cover, and qualitatively assessing the waypoint suitability for outplanting plots. Also, observers recorded desirable species such as acroporids, orbicellids, long spine urchins and other ESA enlisted species.
Preliminary results of our benthic assessment. In Punta Maguey, the most prevalent reef types were aggregated patch reef (n = 15), fringing patch reef (n = 14), and aggregated reef (n = 11). In contrast, in Punta Tampico, aggregated patch reef dominated (n = 28), followed by aggregated reef (n = 8). Similarly, reef complexity was more variable in Punta Maguey than in Punta Tampico. However, both sites were dominated by reefs with low to moderate reef structural complexity.
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Fieldwork 5 & 6: Selection of areas that will serve to evaluate the success of the project
The objective of these two fieldwork sections was to demarcate the areas that will serve to evaluate the success of the project. We aim to quantify the effect of increased reef-three-dimensional structure on fish and coral community and coral outplants' demographic performance. We used the data collected during Fieldwork # 4 (e.g., benthic composition) to select the locations. The selection was based on the absence/very low abundance of ESA listed corals, the presence of suitable areas for coral outplanting, and areas of low topographic relief. Sandy areas and areas where the reef substrate did not cover at least 400m2 were excluded. Twelve localities were selected per site. At each locality, four 10m x 10m (100 m2) transects were demarcated. Each plot was identified with a numbered tag, a rod at the beginning of the transect, and two nails at the beginning of each plot's corner. Of the twelve transects, three will be impacted using only coral outplants; three will be impacted using only 3D-printed corals; 3 will be impacted by combining coral outplants + 3D-printed corals, and 3 will serve as controls (no coral outplants nor 3D-printed corals). At the end of the fieldwork sections, 12 points were finished at Punta Maguey and 12 at Punta Tampico.
Yellow squares indicate sites selected for the experimental phase of the project.
Fieldwork 7: Assessment of coral reef benthic communities
These images show a glimpse of the reef substrate at the restoration sites. Although there were areas of the reef substrate free of competing algae (left), fleshy algae dominated the reef substrate at most stations (right).
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From December 4th to the 6th, we collected a more compressive data set to evaluate the sites' conditions. Information was collected from 15 1m2 quadrats placed within each of the 100m2 quadrats for a total of 60 m2, representing 15% of the area to be restored. Photographs of each 15 1m2 quadrats were taken and are being analyzed to estimate, among other metrics, coral cover, benthic biodiversity, and coral recruits. The data will serve as the baseline (before impact) to compared changes in benthic community structure after coral outplanting. So far, macroalgae is covering more benthic substrate than corals in the two localities. Indeed, the mean coral cover did not exceed 25% at any of the localities. The low coral cover is not surprising as many coral populations were extirpated by the hurricanes. Most dead corals were colonized by algae, contributing to the high percentage of macroalgae cover quantified during the preliminary analyses.
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Fieldwork 8: Assessment of coral reef fish community structure (I)
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The main goal of this field trip was to collect the baseline information on fish community structure. The baseline information will be used to compare the impact of reef restoration on fish abundance, diversity, and biomass. In total, 11 sites have been visited at Punta Maguey. At each locality, stationary visual censuses were carried out in each of the four 10 x 10 m (100 m2) quadrants by modifying the stationary visual census developed by Bohnsack and Bannerot (1986). Each visual census was carried out during 10 minutes of observation, all the fish were identified, quantified, and their sizes were estimated. The fish length data were used to calculate the biomass. In total, 44 stationary visual censuses have already been obtained.
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Dr. Edwin A. Hernandez-Delgado collecting fish data.
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Fieldwork 9: Assessment of coral reef fish community structure (II) & Digital reef rugosity estimates (I)
The purpose of this fieldwork was to continue with the fish surveys (at Pta. Tampico) and collect data on coral recruitment that were started during fieldwork 7. We also started to measure the reef complexity using digital level gauges (see Dustan et al. 2013). Using digital gauges allow us to record data every second, see Dustan et al. 2013 for a complete description and protocol of the methodology. In total, eight stations were completed in Pta Tampico. The data obtained from the sensors will be validated using the traditional chain technique.
Fieldwork 10: Assessment of coral reef fish community structure (III), Digital reef rugosity estimates (II), Permanent quadrats (I) & Testing 3D-artificial corals
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This fieldwork section aimed to finish the pre-restoration fish and coral recruitment surveys while continuing to quantify reef complexity. We also started to establish the permanent quadrats that will be used to estimate changes in the percent of coral cover and coral recruitment rates. Poor weather condition prevents us from finishing the proposed activities.
A prototype of the 3D-printed corals that will be used to promote fish abundance was deployed at one of our coral propagation units to test, among other things, manageability. |
An example of one 3D-printed cora prototype that will be used to attract reef fish to the restoration areas.
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Fieldwork 10: Photomosaics
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We will take advantage of digital imaging, software, and computing advances to collect and create a highly detailed composite, large-area orthorectified photomosaics of coral reefs. Photomosaics is a form of photogrammetry that can be used to generate 2-dimensional (and 3-dimensional) images of a given area by putting together 100s to 1,000s still images taken from standard cameras. High-resolution photomosaics will be used to extract information in percent cover, species composition, colony size structures, and incidence of disease or bleaching/recent mortality. During this fieldwork Dr. Rolando Santos visited some of the locations that will be restored and collected images that will be used to generate a 2-d mosaics describing the pre-restoration condition.
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