Hartill ÉC et al. (2020), Deep coral habitats of Glacier Bay National Par...

ECB-ART-49701

PLoS One 2020 Jan 01;158:e0236945. doi: 10.1371/journal.pone.0236945.

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Deep coral habitats of Glacier Bay National Park and Preserve, Alaska.

Hartill ÉC , Waller RG , Auster PJ .

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Glacier Bay National Park and Preserve (GBNPP) in Southeast Alaska is a system of glaciated fjords with a unique and recent history of deglaciation. As such, it can serve as a natural laboratory for studying patterns of distribution in marine communities with proximity to glacial influence. In order to examine the changes in fjord-based coral communities, underwater photo-quadrats were collected during multipurpose dives with a remotely operated vehicle (ROV) in March of 2016. Ten sites were chosen to represent the geochronological and oceanographic gradients present in GBNPP. Each site was surveyed vertically between 100 and 420 meters depth and photo-quadrats were extracted from the video strip transects for analysis. The ROV was equipped with onboard CTD which recorded environmental data (temperature and salinity), in order to confirm the uniformity of these characteristics at depth across the fjords. The percent cover and diversity of species were lowest near the glaciated heads of the fjords and highest in the Central Channel and at the mouths of the fjords. Diversity is highest where characteristics such as low sedimentation and increased tidal currents are predominant. The diverse communities at the mouths of the fjords and in the Central Channel were dominated by large colonies of the Red Tree Coral, Primnoa pacifica, as well as sponges, brachiopods, multiple species of cnidarians, echinoderms, molluscs and arthropods. The communities at the heads of the fjords were heavily dominated by pioneering species such as brachiopoda, hydrozoan turf, the encrusting stoloniferan coral Sarcodyction incrustans, and smaller colonies of P. pacifica. This research documents a gradient of species dominance from the Central Channel to the heads of the glaciated fjords, which is hypothesized to be driven by a combination of physical and biological factors such as glacial sedimentation, nutrient availability, larval dispersal, and competition.

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	Fig 1. Map of studies sites in Glacier Bay National Park & Preserve.The ten study sites are marked: far sites (>50km from tidewater glaciers), mid sites (20-40km from tidewater glaciers), and near sites (<10km from tidewater glaciers). Sills are indicated with arrows, tidewater glaciers are represented by blue boxes.
	Fig 2. Species accumulations curves and richness estimates.(a) The species accumulation curve, S observed, shows the average observed species for each zone (near, mid and far) with standard deviation error bars present. (b) Average CHAO 1 richness estimator curves for each zone (near, mid and far). For species accumulation curves and CHAO 1 richness estimates of individual sites see Supporting Information.
	Fig 3. Exemplar epifaunal taxa observed.(a) large Primnoa pacifica colony (b) anemones Cribrinopsis sp. (c) encrusting stoloniferan coral Sarcodyction incrustans (d) close up of hydrozoan turf and arrows point to solitary cup coral Caryophyllia arnoldi (e) arrows point to small (<0.25 m) P. pacifica colony and brachiopods Laqueus californicus (f) arrows point to the snails Fusitriton oregonensis laying egg capsules as well as a blood star Henricia sp.–there are also C. arnoldi in this image. (h) Brittle star (Ophiopholis sp.) arms and an octopus, Enteroctopus dofleini, under barnacles, Chirona evermanni (i) decorated warbonnet Chirolophis decorates amongst branches of a P. pacifica colony (j) snow crab Chionoecetes sp. in a large P. pacifica colony (k) P. pacifica colony with an aggregation of juvenile Pacific cod Gadus macrocephalus, also in the image are barnacles (C. evermanni), an anemone (Cribrinopsis sp.), and the predatory nudibranch Tritonia diodema (l) red banded rockfish Sebastes babcocki over demospongiae and two snow crabs (Chionoectessp.) (m) bigmouth sculpin Hemitripterus bolini stationary on edge of P. pacifica branches. Scale bars are 10cm unless otherwise noted.
	Fig 4. Species dominance based on proportion at each site.The sites in this graph are organized by proximity to glacial input (site J1 is closest to a tidewater glacier and site C2 is the furthest).
	Fig 5. Non-metric multidimensional scaling plot.This graph represents the nMDS analysis in two-dimensional space. The nMDS used a Bray-Curtis similarity matrix calculated from percent coverage data that were standardized and square-root transformed. Green circles indicate 70% similarity.
	Fig 6. Site similarity dendrogram.This complete-linkage CLUSTER analysis dendrogram was constructed from a Bray-Curtis similarity matrix calculated from percent coverage data, which were standardized and square-root transformed for analysis.

References [+] :

Graham, Changing role of coral reef marine reserves in a warming climate. 2020, Pubmed