Symbiont Diversity of Zooxanthellae (Symbiodinium Spp.) In Porities Astreoides and Montastraea Cavernosa from a Reciprocal Transplant in the Lower Florida Keys

In recent years, coral reefs worldwide have suffered high mortality rates due to coral bleaching, a phenomenon contributing to a 40% decrease in coral cover in the Florida Keys since the 1997/98 El Niño event. In the Florida Keys, coral from inshore reefs are known to be more thermotolerant than their conspecifics from offshore reefs but the mechanism behind this difference is unclear. In this study we conducted a two-year, reciprocal transplant of Porites astreoides and Montastraea cavernosa from an inshore and offshore reef in the lower Florida Keys to determine if changes in the dominant symbiotic algae (Symbiodinium spp.) could explain variation in holobiont tolerance as well as to assess the possibility of acclimatization to a changing stress regime. Increased complexity and diversity was demonstrated in the composition of Symbiodinium spp. from both coral species collected at the offshore reef when compared to conspecifics collected inshore. As a result of this complexity, the offshore reef samples displayed higher numbers of transitions of zooxanthellae subclade types between seasons, while inshore fragments demonstrated more stability and may explain previously measured thermotolerance. Additionally, the known thermotolerant subclade type D1 was associated with one M. cavernosa fragment from the inshore reef. When fragments were transplanted, compositional patterns of Symbiodinium spp. were retained from site of collection, indicating a lack of acclimatization to a new environment over the lengthy two-year experiment. These results demonstrate variability in the dominant Symbiodinium spp. of P. astreoides and M. cavernosa conspecifics from inshore and offshore reefs in the lower Florida Keys and point to possible patterns in holobiont thermotolerance. This variability may be key to the continued persistence of these species in the face of climate change, but future studies are needed to determine the mechanisms and range in which these subclade types withstand thermal stress

Corals and Their Potential Applications to Integrative Medicine

Over the last few years, we have pursued the use and exploitation of invertebrate immune systems, most notably their humoral products, to determine what effects their complex molecules might exert on humans, specifically their potential for therapeutic applications. This endeavor, called “bioprospecting,” is an emerging necessity for biomedical research. In order to treat the currently “untreatable,” or to discover more efficient treatment modalities, all options and potential sources must be exhausted so that we can provide the best care to patients, that is, proceed from forest and ocean ecosystems through the laboratory to the bedside. Here, we review current research findings that have yielded therapeutic benefits, particularly as derived from soft and hard corals. Several applications have already been demonstrated, including anti-inflammatory properties, anticancer properties, bone repair, and neurological benefits

Stress Resistance and Adaptation of the Aquatic Invasive Species Tubastraea Coccinea (Lesson, 1829) to Climate Change and Ocean Acidification

A great number of studies published on long-term ocean warming and increased acidification have forecasted changes in regional biodiversity preempted by aquatic invasive species (AIS). The present paper is focused on invasive Tubastraea coccinea (TC), an azooxanthellate AIS coral thriving in regions of the Gulf of Mexico, which has shown an ability to invade altered habitats, including endemic Indo-Pacific T. coccinea (TCP) populations. To determine if invasive TC are more stress resistant than endemic Indo-Pacific T. coccinea (TCP), authors measured tissue loss and heat shock protein 70 (HSP70) expression, using a full factorial design, post exposure to changes in pH (7.5 and 8.1) and heat stress (31 °C and 34 °C). Overall, the mean time required for TCP to reach 50% tissue loss (LD50) was less than observed for TC by a factor of 0.45 (p < 0.0003). Increasing temperature was found to be a significant main effect (p = 0.004), decreasing the LD50 by a factor of 0.58. Increasing acidity to pH 7.5 from 8.1 did not change the sensitivity of TC to temperature; however, TCP displayed increased sensitivity at 31 °C. Increases in the relative density of HSP70 (TC) were seen at all treatment levels. Hence, TC appears more robust compared to TCP and may emerge as a new dominant coral displacing endemic populations as a consequence of climate change

Responses to High Seawater Temperatures in Zooxanthellate Octocorals

<div><p>Increases in Sea Surface Temperatures (SSTs) as a result of global warming have caused reef-building scleractinian corals to bleach worldwide, a result of the loss of obligate endosymbiotic zooxanthellae. Since the 1980’s, bleaching severity and frequency has increased, in some cases causing mass mortality of corals. Earlier experiments have demonstrated that zooxanthellae in scleractinian corals from three families from the Great Barrier Reef, Australia (Faviidae, Poritidae, and Acroporidae) are more sensitive to heat stress than their hosts, exhibiting differential symptoms of programmed cell death – apoptosis and necrosis. Most zooxanthellar phylotypes are dying during expulsion upon release from the host. The host corals appear to be adapted or exapted to the heat increases. We attempt to determine whether this adaptation/exaptation occurs in octocorals by examining the heat-sensitivities of zooxanthellae and their host octocoral alcyonacean soft corals – <em>Sarcophyton ehrenbergi</em> (Alcyoniidae), <em>Sinularia lochmodes</em> (Alcyoniidae), and <em>Xenia elongata</em> (Xeniidae), species from two different families. The soft coral holobionts were subjected to experimental seawater temperatures of 28, 30, 32, 34, and 36°C for 48 hrs. Host and zooxanthellar cells were examined for viability, apoptosis, and necrosis (<em>in hospite</em> and expelled) using transmission electron microscopy (TEM), fluorescent microscopy (FM), and flow cytometry (FC). As experimental temperatures increased, zooxanthellae generally exhibited apoptotic and necrotic symptoms at lower temperatures than host cells and were expelled. Responses varied species-specifically. Soft coral hosts were adapted/exapted to higher seawater temperatures than their zooxanthellae. As with the scleractinians, the zooxanthellae appear to be the limiting factor for survival of the holobiont in the groups tested, in this region. These limits have now been shown to operate in six species within five families and two orders of the Cnidaria in the western Pacific. We hypothesize that this relationship may have taxonomic implications for other obligate zooxanthellate cnidarians subject to bleaching.</p> </div

Effects of seawater temperature on percent necrotic endosymbiotic <i>Symbiodinium</i> and host coral <i>Sinularia lochmodes</i> cells. <i>In-hospite</i>

<p>, collected over a12 h period. Corals exposed to 28 to 36°C treatments. • = 28°C; ○ = 30°C;▾ = 32°C; Δ = 34°C; ▪ = 36°C. Data transformed by arcsine for normalization purposes. <b>Zooxanthellae:</b> No significant linear regressions at 28–34°C (p>0.05); <i>i.e.,</i> linear regression coefficients were not significantly different from “0″. Significant deviations from linearity and non-linear response at 36°C (p<0.001; Y = 21.964+23.434*[1−e^(−0745X)]). <b>Host Cells:</b> No significant linear regressions at 28–32°C (p>0.05); <i>i.e.,</i> regression coefficients were not significantly different from “0”. Significant positive linear regressions at 34–36°C (p<0.05; Y = 0.979X +14.152, and Y = 1.214X +18.952, respectively).</p

Effects of increasing seawater temperature on percent viable endosymbiotic <i>Symbiodinium</i> and host coral <i>Sarcophyton ehrenbergi</i> cells.

<p><b><i>In-hospite</i></b>, collected over a12 h period. Data shown here relate to corals exposed to 28 to 36°C. • = 28°C; ○ = 30°C;▾ = 32°C; Δ = 34°C; ▪ = 36°C. Data transformed by arcsine for normalization purposes. Each point represents the percentage (%) of different cell types analyzed via TEM. Tissues sampled at 3-hr intervals. (a) <b>Zooxanthellae:</b> Significant linear regression in zooxanthellar cells at 28°C and 34°C (p<0.05); Y = 0.843X +49.184, and Y = −2.072+49.688, respectively. Linear trends shown for 30 and 32°C to facilitate comparison (Y = 1.020X +48.679, and Y = −2.243X +59.107, respectively); significant non-linear components at these temperature responses (p<0.05–0.001). Significant non-linear response at 36°C (p<0.001; Y = 13.285+ −46.506*(1−e^[0.838X]). <b>Host Cells:</b> No significant linear or non-linear response at 28°C or 32°C; (slope not significantly different from ‘0′). Significant negative linear response at 34°C (p<0.01; Y = −1.532X +79.187). Significant non-linear components at 30°C and 36°C (p<0.01–0.001); negative linear trends shown into facilitate comparison (Y = −0.762X +84.783, and Y = −3.578X +79.336, respectively).</p

Effects of seawater temperature on percent apoptotic endosymbiotic <i>Symbiodinium</i> and host coral <i>Sarcophyton ehrenbergi</i> cells.

<p>In-hospite, collected over a12 h period. Corals exposed to 28 to 36°C treatments. • = 28°C; ○ = 30°C;▾ = 32°C; Δ = 34°C; ▪ = 36°C. Data transformed by arcsine for normalization purposes. <b>Zooxanthellae:</b> Significant negative linear regressions through time at 28°C and 30°C (p<0.05–0.01; Y = −0.413X +28.824, and Y = −1.236X +28.400, respectively). No significant linear at 32°C or 34°C (p>0.05); <i>i.e.,</i> regression coefficient not significantly different from “0″. Significant non-linear response at 36°C (p<0.001; Y = 16.608+51.899*[1−−e^(−0.575X)]). <b>Host Cells:</b> No significant linear regression for 28°C, 30°C, 32°C, or 34°C through time (p>0.05); <i>i.e.,</i> regression coefficient not significantly different than “0″. Significant non-linear increase at 36°C (p<0.001); linear trend shown to facilitate comparison (Y = 3.068X +9.999).</p

Effects of seawater temperature on percent viable endosymbiotic <i>Symbiodinium</i> and host coral <i>Sinularia lochmodes</i> cells. <i>In-hospite</i>

<p>, collected over a 12 h period. Corals exposed to 28 to 36°C treatments. • = 28°C; ○ = 30°C;▾ = 32°C; Δ = 34°C; ▪ = 36°C. Data transformed by arcsine for normalization purposes. <b>Zooxanthellae:</b> No significant linear regression at any temperature (p>0.05); <i>i.e.,</i> for 28–34°C, regression coefficient not significantly different than “0″. Significant non-linear components at 28°C, 32°C, 34°C, and 36°C (p<0.05–0.001); linear trends shown in the first three of these temperature treatments to facilitate comparison (Y = 0.386X +53.266, Y = 0.393X +59.393, and Y = 0.169X +54.428, respectively). 36°C exponential decay response described by Y = 7.894+45.820*(1−e^[−0.674X]). <b>Host Cells:</b> No significant linear regression for 28°C, 30°C, or 32°C through time (p>0.05); <i>i.e.,</i> regression coefficient not significantly different than “0”. Significant negative linear regression at 34°C (p<0.05; Y = −1.149X +72.204). Highly significant non-linear negative response at 36°C (p<0.001; Y = 29.058+43.441*[1-e^(−0.407X)]).</p