Overfishing remains a threat to coral reef fishes worldwide, with large carnivores often disproportionately vulnerable. Marine protected areas (MPAs) can restore fish populations and biodiversity, but their effect has been understudied in mesophotic coral ecosystems (MCEs), particularly in the Coral Triangle. Videos were analysed from baited remote underwater video systems deployed in 2016 to investigate the assemblage structure of large carnivorous fishes at shallow (4–12 m) and mesophotic (45–96 m) depths in two of the largest and most isolated MPAs in the Philippines: an uninhabited, fully no‐take MPA enacted in 1988 (Tubbataha Reefs Natural Park) and an archipelagic municipality surrounded by an extensive but not fully no‐take MPA declared in 2016 (Cagayancillo). Taxa focused on were groupers (Serranidae), snappers (Lutjanidae), emperors (Lethrinidae), jacks (Carangidae) and the endangered Mean abundance and species richness were not greater in TRNP than in Cagayancillo regardless of depth despite long‐term protection in the former. Limited impacts of fishing in Cagayancillo may explain this result. Differentiation of fish assemblages was evident between TRNP and Cagayancillo but more obvious between depths at each location, probably due more to habitat than MPA effects. In Cagayancillo, overall carnivorous reef fish, grouper and jack mean abundance were 2, 2 and 10 times higher, respectively, at mesophotic depths, suggesting that MCEs can serve as deep refugia from fishing. These findings of differentiation between depths and higher abundance of certain taxa in mesophotic depths emphasize that MCEs are distinct from shallow reefs, serve as important habitat for species susceptible to overfishing and, thus, must be explicitly included in the design of MPAs. This study also highlights the value of maintaining strict protection of MPAs like TRNP for the Coral Triangle and an opportunity to safeguard intact fish assemblages in Cagayancillo by expanding its no‐take zones.
Large-scale invasion of western Atlantic mesophotic reefs by lionfish potentially undermines culling-based management
The detrimental effects of invasive lionfishes
(Pterois volitans and Pterois miles) on western
Atlantic shallow reefs are well documented, including
declines in coral cover and native fish populations,
with disproportionate predation on critically endangered
reef fish in some locations. Yet despite individuals
reaching depths[100 m, the role of mesophotic
coral ecosystems (MCEs; reefs 30–150 m) in lionfish
ecology has not been addressed. With lionfish control
programs in most invaded locations limited to 30 mby
diving restrictions, understanding the role of MCEs in
lionfish distributions remains a critical knowledge gap
potentially hindering conservation management. Here
we synthesise unpublished and previously published
studies of lionfish abundance and body length at paired
shallow reef (0–30 m) and MCE sites in 63 locations
in seven western Atlantic countries and eight sites in
three Indo-Pacific countries where lionfish are native.
Lionfish were found at similar abundances across the
depth gradient from shallow to adjacent MCEs, with
no difference between invaded and native sites. Of the
five invaded countries where length data were available
three had larger lionfish on mesophotic than
shallow reefs, one showed no significant difference,
while the fifth represented a recently invaded site. This
suggests at least some mesophotic populations may
represent extensions of natural ontogenetic migrations.
Interestingly, despite their shallow focus, in
many cases culling programs did not appear to alter
abundance between depths. In general, we identify
widespread invasive lionfish populations on MCE that
could be responsible for maintaining high densities of
lionfish recruits despite local shallow-biased control
programs. This study highlights the need for management
plans to incorporate lionfish populations below
the depth limit of recreational diving in order to
address all aspects of the local population and
maximise the effectiveness of control efforts.
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- Award ID(s):
- 1632348
- NSF-PAR ID:
- 10059880
- Author(s) / Creator(s):
- ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more »
- Date Published:
- Journal Name:
- Biological invasions
- Volume:
- 19
- Issue:
- 3
- ISSN:
- 1387-3547
- Page Range / eLocation ID:
- 939-954
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Cheilinus undulatus -
Abstract Background: Globally, shallow-water coral reef biodiversity is at risk from a variety of threats, some of which may attenuate with depth. Mesophotic coral ecosystems (MCEs), occurring from 30 to 40 m and deeper in tropical locations, have been subject to a surge of research this century. Though a number of valuable narrative reviews exist, a systematic quantitative synthesis of published MCE studies is lacking. We conducted a systematic review to collate mesophotic research, including studies from the twentieth century to the present. We highlight current biases in research effort, regarding locations and subject matter, and suggest where more attention may be particularly valuable. Following a notable number of studies considering the potential for mesophotic reefs to act as refuges, it is important to know how comprehensive these sources of recruits and organisms capable of moving to shallow water reefs may be. Methods: We search seven sources of bibliographic data with two search strings, as well as personal libraries. Articles were included if they contained species presence data from both shallower and deeper than 30 m depth on tropical coral reefs. Studies were critically appraised based on the number of species identified and balanced sampling effort with depth. Maximum and minimum depths per species were extracted from each study, along with study region and taxon. We quantified the degree of community overlap between shallow tropical reefs (< 30 m) and reefs surveyed at the same locations below 30 m. Proportions of shallow species, across all studied taxa, observed deeper than 30 m were used to generate log odds ratios and passed to a mixed-effects model. Study location and taxon were included as effect modifiers. Funnel plots, regression tests, fail safe numbers, and analysis of a high validity subgroup contributed to sensitivity analyses and tests of bias. Results: Across all studies synthesised we found two-thirds of shallow species were present on mesophotic reefs. Further analysis by taxon and broad locations show that this pattern is influenced geographically and taxonomically. Community overlap was estimated as low as 26% and as high as 97% for some cases. Conclusions: There is clear support for the hypothesis that protecting mesophotic reefs will also help to conserve shallow water species. At the same time, it is important to note that this study does not address mesophotic-specialist communities, or the ecological forces which would permit refuge dynamics. As we limit our analysis to species only present above 30 m it is also possible diversity found exclusively deeper than 30 m warrants protection in its own right. Further research into relatively ignored taxa and geographic regions will help improve the design of protected areas in future. Keywords: Depth, Community structure, Biodiversity, Coral reefs, Twilight zone, Refugemore » « less
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Mesophotic coral reefs, currently defined as deep reefs between 30 and 150 m, are linked physically and biologically to their shallow water counterparts, have the potential to be refuges for shallow coral reef taxa such as coral and sponges, and might be a source of larvae that could contribute to the resiliency of shallow water reefs. Mesophotic coral reefs are found worldwide, but most are undescribed and understudied. Here, we review our current knowledge of mesophotic coral reefs and their functional ecology as it relates to their geomorphology, changes in the abiotic environment along depth gradients, trophic ecology, their reproduction, and their connectivity to shallow depths. Understanding the ecology of mesophotic coral reefs, and the connectivity between them and their shallow water counterparts, is now a primary focus for many reef studies as the worldwide degradation of shallow coral reefs, and the ecosystem services they provide, continues unabated.more » « less
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Abstract Mesophotic reefs (30‐150 m) have been proposed as potential refugia that facilitate the recovery of degraded shallow reefs following acute disturbances such as coral bleaching and disease. However, because of the technical difficulty of collecting samples, the connectivity of adjacent mesophotic reefs is relatively unknown compared with shallower counterparts. We used genotyping by sequencing to assess fine‐scale genetic structure of Montastraea cavernosa at two sites at Pulley Ridge, a mesophotic coral reef ecosystem in the Gulf of Mexico, and downstream sites along the Florida Reef Tract. We found differentiation between reefs at Pulley Ridge (~68 m) and corals at downstream upper mesophotic depths in the Dry Tortugas (28–36 m) and shallow reefs in the northern Florida Keys (Key Biscayne, ~5 m). The spatial endpoints of our study were distinct, with the Dry Tortugas as a genetic intermediate. Most striking were differences in population structure among northern and southern sites at Pulley Ridge that were separated by just 12km. Unique patterns of clonality and outlier loci allele frequency support these sites as different populations and suggest that the long‐distance horizontal connectivity typical of shallow‐water corals may not be typical for mesophotic systems in Florida and the Gulf of Mexico. We hypothesize that this may be due to the spawning of buoyant gametes, which commits propagules to the surface, resulting in greater dispersal and lower connectivity than typically found between nearby shallow sites. Differences in population structure over small spatial scales suggest that demographic constraints and/or environmental disturbances may be more variable in space and time on mesophotic reefs compared with their shallow‐water counterparts.more » « less
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Abstract Mesophotic coral ecosystems (MCEs) are tropical reefs found at depths of ~30–150 m, below the region most heavily impacted by heat stress and other disturbances. Hence, MCEs may serve as potential refugia for threatened shallow reefs, but they also harbour depth‐endemic fauna distinct from shallow reefs. Previous studies have characterized biodiversity patterns along depth gradients, but focussed primarily on conspicuous taxa (fishes, corals, etc.). Environmental DNA (eDNA) metabarcoding offers a more holistic approach to assess biodiversity patterns across the tree of life. Here, we use three metabarcoding assays targeting fishes (16S rRNA), eukaryotes (18S rDNA) and metazoans (COI) to assess biodiversity change from the surface to ~90 m depth across 15‐m intervals at three sites within the Hawaiian Archipelago. We observed significant community differences between most depth zones, with distinct zonation centred at 45–60 m for eukaryotes and metazoans, but not for fishes. This finding may be attributable to the higher mobility of reef fishes, although methodological limitations are likely a contributing factor. The possibility for MCEs to serve as refugia is not excluded for fishes, but invertebrate communities >45 m are distinct, indicating limited connectivity for the majority of reef fauna. This study provides a new approach for surveying biodiversity on MCEs, revealing patterns in a much broader context than the limited‐taxon studies that comprise the bulk of our present knowledge.
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/DOI 10.1007/s10530-016-1358-0
