Porites superfusa mortality and recovery from a bleaching event at Palmyra Atoll, USA.

BackgroundThe demography of a coral colony is not a binary trajectory of life and death. Based on the flexibility afforded by colonial organization, most reef-building corals employ a variety of dynamic survival strategies, including growth and shrinkage. The demographic flexibility affects coral size, shape and reproductive output, among other factors. It is thus critical to quantify the relative importance of key dynamics of recruitment, mortality, growth and shrinkage in changing the overall cover of coral on a reef.MethodsUsing fixed photographic quadrats, we tracked the patterns of change in the cover of one common central Pacific coral, Porites superfusa, before and after the 2009 ENSO event.ResultsCoral colonies suffered both whole and partial colony mortality, although larger colonies were more likely to survive. In subsequent years, recruitment of new colonies and regrowth of surviving colonies both contributed to the modest recovery of P. superfusa.DiscussionThis study is unique in its quantitative comparisons of coral recruitment versus regrowth during periods of areal expansion. Our data suggest that recovery is not limited simply to the long pathway of settlement, recruitment and early growth of new colonies but is accelerated by means of regrowth of already established colonies having suffered partial mortality

Incidence of lesions on Fungiidae corals in the eastern Red Sea is related to water temperature and coastal pollution

Author Posting. © The Author(s), 2014. This is the author's version of the work. It is posted here by permission of Elsevier for personal use, not for redistribution. The definitive version was published in Marine Environmental Research 98 (2014): 29-38, doi:10.1016/j.marenvres.2014.04.002.As sea surface temperatures rise and the global human population increases, large-scale field observations of marine organism health and water quality are increasingly necessary. We investigated the health of corals from the family Fungiidae using visual observations in relation to water quality and microbial biogeochemistry parameters along 1300 km of the Red Sea coast of Saudi Arabia. At large scales, incidence of lesions caused by unidentified etiology showed consistent signs, increasing significantly from the northern to southern coast and positively correlated to annual mean seawater temperatures. Lesion abundance also increased to a maximum of 96% near the populous city of Jeddah. The presence of lesioned corals in the region surrounding Jeddah was strongly correlated with elevated concentrations of ammonium and changes in microbial communities that are linked to decreased water quality. This study suggests that both high seawater temperatures and nutrient pollution may play an indirect role in the formation of lesions on corals.This research was supported by Award No. USA 00002 to K. Hughen by King Abdullah University of Science and Technology (KAUST) and a WHOI Ocean Life Institute postdoctoral scholar fellowship to A. Apprill

The life and death of perforate corals at Palmyra Atoll, USA: micro-community structure within the skeleton.

Coral reefs have been part of the earth’s oceans since the Mesozoic Era, over 200 million years ago. In recent decades, however, reefs have been progressively suffering as a result of human activities. However, coral species vary in their response to ecological disturbance. The work described here examines aspects of the biology of two central Pacific species: Porites superfusa, a small encrusting coral, and Acropora cytherea, a dynamic, massive table coral. Both species are perforate corals, with skeletons permeated with an extensive canal system partially lined with living coral tissue. Thus far, the question of whether the perforate coral condition conveys functional advantages lacking in corals with imperforate (relatively dense) skeletons has been overlooked. The present work supported with field work and sample collections at Palmyra Atoll, Line Islands, USA, during approximately annual visits of several weeks each from 2012 to 2016. The reef is protected from fishing and local pollution but still exposed to wide-scale disturbances like climate change (especially evident in warm water bleachings in 2009, 2015, 2016). This dissertation explores the importance of coral regrowth, endoliths and adjacent epiliths to reef recovery dynamics. Long-term changes in coverage of Porites superfusa were followed in a time series of high-resolution photoquadrats that demonstrated new settlement as well as changes in existing colonies (growth, partial mortality, death, and “death” followed by resurrection). Partial mortality and survival was usually observed in larger individuals, whereas smaller individuals tended to grow progressively or apparently die out completely. However, quite often a new small individual would appear in the area where a colony had died previously in the time series. Although settlement of planula larvae from the water column could not be completely ruled out, the source of new growth could have been from a small amount of living tissue cryptically surviving in or on the “dead” colony. Further work would be required to see if new growth was seeded by small regions of viable tissue. For the other perforate coral in this dissertation, Acropora cytherea, the distribution of living tissues was studied in the canals permeating the skeleton in healthy and evidently dead (algae-covered) regions of the colony. Core samples were studied by scanning electron and light microscopy. In healthy regions, the living coral tissues lined only the intraskeletal canals to a depth of several millimeters from the surface of the colony. In healthy parts of the colony, the canals more than a few millimeters deep in the colony were bounded not by living coral tissues, but with calcareous skeleton. Although the coral skeleton was riddled with endoliths (algae, fungi and bacteria), they were relatively rarely observed in the canal space. In regions where the living part of the colony was covered over with turf algae and other invading organisms, these endoliths were detected, along with abundant sediment, packing the most superficial intracellular canals; surprisingly the canals deeper beneath the overgrown region were free of such extraneous material. In the light of these results, one can speculate that fluid (driven by flagella in the relatively superficial healthy part of the colony) might percolate throughout the intraskeletal canal system, even in regions underlying places overgrown with algae and other organisms. Such a flow could conceivably distribute nutrients or coral cells to regions where they might influence the repair of the locally overgrown parts of the colony overlying them. Light microscopic and molecular techniques (internal transcribed spacers, ITS and 18S cDNA) were combined to provide an overview of the overgrowing and endolithic organisms associated with A. cytherea. The sampled regions of the colony were living, recently dead (near living coral tissue) or long dead (far from living coral tissue). The data permitted mostly genus-level identification of macroalgae, endolithic and epilithic algae, and endolithic fungi. A comparison between living, recently dead, and long dead samples demonstrated a succession in community composition of the algae. Even so, there were notable similarities in the genera of endolithic fungi present in the skeleton of living and dead regions of the colony. The endolithic communities within the coral may be a link between live and dead coral in the calcium carbonate structures. This might reflect a uniformity and connectivity maintained by the deep circulation within the unobstructed lumens of the intraskeletal canal system throughout the colony, even beneath superficially overgrown areas. In sum, the results of the different parts of this dissertation point to the need for further studies of the recently neglected perforate skeleton character and connecting endoliths and their possible relationship to resilience of some perforate corals. Understanding partial survival and dead coral skeleton may hold additional hints at maintaining and protecting coral reef ecosystems

Porites superfusa mortality and recovery from a bleaching event at Palmyra Atoll, USA.

BackgroundThe demography of a coral colony is not a binary trajectory of life and death. Based on the flexibility afforded by colonial organization, most reef-building corals employ a variety of dynamic survival strategies, including growth and shrinkage. The demographic flexibility affects coral size, shape and reproductive output, among other factors. It is thus critical to quantify the relative importance of key dynamics of recruitment, mortality, growth and shrinkage in changing the overall cover of coral on a reef.MethodsUsing fixed photographic quadrats, we tracked the patterns of change in the cover of one common central Pacific coral, Porites superfusa, before and after the 2009 ENSO event.ResultsCoral colonies suffered both whole and partial colony mortality, although larger colonies were more likely to survive. In subsequent years, recruitment of new colonies and regrowth of surviving colonies both contributed to the modest recovery of P. superfusa.DiscussionThis study is unique in its quantitative comparisons of coral recruitment versus regrowth during periods of areal expansion. Our data suggest that recovery is not limited simply to the long pathway of settlement, recruitment and early growth of new colonies but is accelerated by means of regrowth of already established colonies having suffered partial mortality

Closed Spillway with side channel : Design of inlet to shaft / sloping tunnel

Det har tidlegare vore utført modellforsøk som har studert kapasiteten til sidekanalen i eit lukka flaumløp. Denne oppgåva har til hensikt å fortsetje arbeidet, og fokuserer på kapasiteten i overgangen mellom sidekanal og tunnel.For å kunne undersøke kapasiteten så grundig som mogleg vart det utvikla ein modulbasert modell, som tillet systematisk variasjon av horisontalvinklar, vertikal vinklar og utviding av sidekanal. Alle delar kan stillast inn med stor grad av nøyaktigheit. Med denne grada av fridom i modellen, vart det mogleg å undersøke enkelte parameterar i forsøka. sidan alle forsøka vart gjort slik at dei har eit søsterforsøk med berre ein parameter i forskjell, er det mogleg å undersøke kva verknad kvar enkelt parameter har på kapasiteten.Kapasiteten i overgangen mellom sidekanalen og avløpskanalen i modellen vart undersøkt ved å justere horisontalvinklar og vertikal vinklar separat. Slik at dei enkelte parameterane i så stor grad som mogleg kunne isolerast, og undersøkast.Det teoretiske grunnlaget for å berekne kapasiteten i eit overløp er noko avgrensa. Derfor vart resultata frå modellforsøket samanlikna med likningar for berekning av kulvertkapasitet.Resultatet frå modellforsøket viser at den beste utforminga er så slak horisontal overgang frå sidekanaltverrsnittet til tunnel tverrsnitt som mogleg. Den vertikale vinkelen på avløpet bør vere så bratt som mogleg, men ikkje brattare enn 45°.Dette er ikkje heilt i samsvar med kulvertberekningane, men resultata viser at berekningsmåten kan tilpassast til eit lukka flaumløp.For flaumløpet på Helgedalsdammen vert det vurdert at det ikkje kan trekkast nokon siker konklusjonar frå dei generelle modellforsøka utan å verifisere dei i eigne modellforsøk av det aktuelle flaumløpet

Depth variation in anemone bleaching at Papua New Guinea.

<p>Mean depth (±SE) of bleached and unbleached host anemones during the major bleaching event at Papua New Guinea in 2009. (A) <i>Heteractis crispa</i> and (B) <i>Stichodactyla haddoni</i>.</p

Ranked linear mixed-effects models of anemone size explained by date, bleaching category (bleach_cat) and the interaction between these two variables.

<p>All models have individual colony coded as a random effect (1|id). The models are ranked against the intercept-only model (NULL model). Also shown is the number of estimable model parameters (<i>k</i>), maximum log-likelihood (LL), Akaike’s information criterion corrected for small samples (AIC<i>_c</i>), the difference in AIC<i>_c</i> for each model from the top-ranked model (ΔAIC) and the model weight (<i>w</i>AIC<i>_c</i>).</p

Spatial variation in anemone bleaching.

<p>Number of bleached (white bars) and unbleached (black bars) host anemones encountered in surveys at different sites during the major anemone bleaching events. Data are presented for: (A) <i>Heteractis crispa</i> and (B) <i>Stichodactyla haddoni</i> at Papua New Guinea in 2009; (C) <i>Cryptodendrum adhaesivum</i> and (D) <i>H. magnifica</i> at Christmas Island, 2010; (E) <i>Entacmaea quadricolor</i> at Keppel Islands, 2011; (F) <i>C. adhaesivum</i> and (G) <i>H. magnifica</i> at Christmas Island, 2005. Abbreviations for site names are provided in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0070966#pone.0070966.s001" target="_blank">Table S1</a>.</p