Microbiome signatures in Acropora cervicornis are associated with genotypic resistance to elevated nutrients and heat stress

Coral Reefs - The staghorn coral, Acropora cervicornis, was once abundant in the Caribbean, but now is listed as critically endangered. To recover A. cervicornis populations, restoration efforts...     

Effects of elevated pCO(2) and/or osmolality on the growth and recombinant tPA production of CHO cells

Carbon dioxide is a by-product of mammalian cell metabolism that will build up in culture if it is not removed from the medium. Increased carbon dioxide levels are generally not a problem in bench-top bioreactors, but inhibitory levels can easily be reached in large-scale vessels, especially if the aeration gas is enriched in oxygen. Due to the equilibrium attained between dissolved CO(2) and bicarbonate, increased pCO(2) is associated with increased osmolality in bioreactors with pH control. While a few preliminary reports indicate that elevated pCO(2) levels can inhibit cell growth and/or recombinant protein production, no comprehensive analysis of the interrelated effects of elevated pCO(2) and osmolality has been published. We have examined the effects of 140, 195, and 250 mm Hg (187, 260, and 333 mbar, respectively) pCO(2) (with and without osmolality control) on the growth of and recombinant tPA production by MT2-1-8 Chinese hamster ovary (CHO) cells. The effects of elevated osmolality were also investigated at the control pCO(2) of 36 mm Hg. Elevated pCO(2) at 310 mOsm/kg osmolality inhibited cell growth in a dose-dependent fashion, with a maximum decrease of 30% in the specific growth rate (mu) at 250 mm Hg. Osmolality alone had no effect on mu, but the combination of elevated pCO(2) and osmolality increased the maximal reduction in mu to 45%. Elevated pCO(2) at 310 mOsm/kg osmolality decreased the specific tPA production rate (q(tPA)) by up to 40% at 250 mm Hg. Interestingly, while increased osmolality decreased q(tPA) significantly at 140 mm Hg pCO(2), it had no effect or even increased q(tPA) at 195 and 250 mm Hg. (c) 1996 John Wiley & Sons, Inc.     

Acropora cervicornis genet performance and symbiont identity throughout the restoration process

Coral Reefs - In the Caribbean, corals are commonly cultured in ocean-based nurseries and outplanted back to reefs for population enhancement. Intraspecific diversity in host and symbiont is an...     

光强转换对不同生长环境下桑树叶片光化学效率的影响

以桑树品种‘蒙古桑’为试验材料,利用叶绿素荧光技术研究了光强转换对生长在不同光强下的桑树叶片实际光化学效率(ΦPSⅡ)、电子传递速率(ETR)和非光化学淬灭(NPQ)的影响,分析了非光化学淬灭(NPQ)3个组分的变化.结果表明:当光强从黑暗或弱光转换到自然光条件下,自然光桑树叶片的光量子转化效率高于弱光叶片,ΦPSⅡ、ETR诱导平衡较快,NPQ诱导呈先升后降趋势.自然光叶片在强光下状态转换淬灭组分(qT)占NPQ的18%,而弱光叶片qT仅占NPQ的7%.与弱光桑树叶片相比,自然光桑树叶片可以通过较高的光量子转化效率和较强的调节激发能在PSⅠ和PSⅡ之间的分配能力来适应光强的变化.     

Effects of elevated pCO2 and osmolality on growth of CHO cells and production of antibody-fusion protein B1: a case study

Partial pressure of CO2 (pCO2) and osmolality as high as 150 mmHg and 440 mOsm/kg, respectively, were observed in large-scale CHO cell culture producing an antibody-fusion protein, B1. pCO2 and osmolality, when elevated to high levels in bioreactors, can adversely affect cell culture and recombinant protein production. To understand the sole impact of pCO2 or osmolality on CHO cell growth, experiments were performed in bench-scale bioreactors allowing one variable to change while controlling the other. Elevating pCO2 from 50 to 150 mmHg under controlled osmolality (about 350 mOsm/kg) resulted in a 9% reduction in specific cell growth rate. In contrast, increasing osmolality resulted in a linear reduction in specific cell growth rate (0.008 h(-1)/100 mOsm/kg) and led to a 60% decrease at 450 mOsm/kg as compared to the control at 316 mOsm/kg. This osmolality shift from 316 to 445 mOsm/kg resulted in an increase in specific production rates of lactate and ammonia by 43% and 48%, respectively. To elucidate the effect of high osmolality and/or pCO2 on the production phase, experiments were conducted in bench-scale bioreactors to more closely reflect the pCO2 and osmolality levels observed at large scale. Increasing osmolality to 400-450 mOsm/kg did not result in an obvious change in viable cell density and product titer. However, a further increase in osmolality to 460-500 mOsm/kg led to a 5% reduction in viable cell density and a 8% decrease in cell viability as compared to the control. Final titer was not affected as a result of an apparent increase in specific production rate under this increased osmolality. Furthermore, the combined effects from high pCO2 (140-160 mmHg) and osmolality (400-450 mOsm/kg) caused a 20% drop in viable cell density, a more prominent decrease as compared to elevated osmolality alone. Results obtained here illustrate the sole effect of high pCO2 (or osmolality) on CHO cell growth and demonstrate a distinct impact of high osmolality and/or pCO2 on production phase as compared to that on growth phase. These results are useful to understand the response of the CHO cells to elevated pCO2 (and/or osmolality) at a different stage of cultivation in bioreactors and thus are valuable in guiding bioreactor optimization toward improving protein production.     

Effects of elevated pCO2 on the photosynthetic performance of the sea ice diatoms Navicula directa and Navicula glaciei

Journal of Applied Phycology - Sea ice algal communities are generally dominated by pennate diatoms, which commonly occur at the ice-water interface and in brine channels. They also make a...     

Arbuscular mycorrhiza infection enhances the growth response of Lolium perenne to elevated atmospheric pCO(2)

Elevated atmospheric pCO(2) increases the C-availability for plants and thus leads to a comparable increase in plant biomass production and nutrient demand. Arbuscular mycorrhizal fungi (AMF) are considered to play an important role in the nutrient uptake of plants as well as to be a significant C-sink. Therefore, an increased colonization of plant roots by AMF is expected under elevated atmospheric pCO(2). To test these hypotheses, Lolium perenne L. plants were grown from seeds in a growth chamber in pots containing a silica sand/soil mixture for 9 weeks with and without inoculation with Glomus intraradices (Schenck and Smith). The growth response of plants at two different levels of N fertilization (1.5 or 4.5 mM) combined with ambient (35 Pa) and elevated atmospheric pCO(2) (60 Pa) was compared. The inoculation with G. intraradices, the elevated atmospheric pCO(2) and the high N fertilization treatment all led to an increased plant biomass production of 16%, 20% and 49%, respectively. AMF colonization and high N fertilization increased the plant growth response to elevated atmospheric pCO(2); the plant growth response to high N fertilization was also increased by AMF colonization. The root/shoot ratio was reduced by high N fertilization or elevated atmospheric pCO(2), but was not affected by AMF colonization. The unchanged specific leaf area indicated that if AMF colonization represented an increased C-sink, this was fully covered by the plant. Elevated atmospheric pCO(2) strongly increased AMF colonization (60%) while the high N fertilization had a slightly negative effect. AMF colonization neither improved the N nor P nutrition status, but led to an improved total P uptake. The results underline the importance of AMF for the response of grassland ecosystems to elevated atmospheric pCO(2).     

Effects of elevated pCO2 on the metabolism of a temperate rhodolith Lithothamnion corallioides grown under different temperatures

Coralline algae are considered among the most sensitive species to near future ocean acidification. We tested the effects of elevated pCO₂ on the metabolism of the free‐living coralline alga Lithothamnion corallioides (“maerl”) and the interactions with changes in temperature. Specimens were collected in North Brittany (France) and grown for 3 months at pCO₂ of 380 (ambient pCO₂), 550, 750, and 1000 μatm (elevated pCO₂) and at successive temperatures of 10°C (ambient temperature in winter), 16°C (ambient temperature in summer), and 19°C (ambient temperature in summer +3°C). At each temperature, gross primary production, respiration (oxygen flux), and calcification (alkalinity flux) rates were assessed in the light and dark. Pigments were determined by HPLC. Chl a, carotene, and zeaxanthin were the three major pigments found in L. corallioides thalli. Elevated pCO₂ did not affect pigment content while temperature slightly decreased zeaxanthin and carotene content at 10°C. Gross production was not affected by temperature but was significantly affected by pCO₂ with an increase between 380 and 550 μatm. Light, dark, and diel (24 h) calcification rates strongly decreased with increasing pCO₂ regardless of the temperature. Although elevated pCO₂ only slightly affected gross production in L. corallioides, diel net calcification was reduced by up to 80% under the 1,000 μatm treatment. Our findings suggested that near future levels of CO₂ will have profound consequences for carbon and carbonate budgets in rhodolith beds and for the sustainability of these habitats.     

Genetic Diversity and Connectivity in the Threatened Staghorn Coral (Acropora cervicornis) in Florida

Over the past three decades, populations of the dominant shallow water Caribbean corals, Acropora cervicornis and A. palmata, have been devastated by white-band disease (WBD), resulting in the listing of both species as threatened under the U.S. Endangered Species Act. A key to conserving these threatened corals is understanding how their populations are genetically interconnected throughout the greater Caribbean. Genetic research has demonstrated that gene flow is regionally restricted across the Caribbean in both species. Yet, despite being an important site of coral reef research, little genetic data has been available for the Florida Acropora, especially for the staghorn coral, A. cervicornis. In this study, we present new mitochondrial DNA sequence data from 52 A. cervicornis individuals from 22 sites spread across the upper and lower Florida Keys, which suggest that Florida''s A. cervicornis populations are highly genetically interconnected (F_ST = −0.081). Comparison between Florida and existing mtDNA data from six regional Caribbean populations indicates that Florida possesses high levels of standing genetic diversity (h = 0.824) relative to the rest of the greater Caribbean (h = 0.701±0.043). We find that the contemporary level of gene flow across the greater Caribbean, including Florida, is restricted ( = 0.117), but evidence from shared haplotypes suggests the Western Caribbean has historically been a source of genetic variation for Florida. Despite the current patchiness of A. cervicornis in Florida, the relatively high genetic diversity and connectivity within Florida suggest that this population may have sufficient genetic variation to be viable and resilient to environmental perturbation and disease. Limited genetic exchange across regional populations of the greater Caribbean, including Florida, indicates that conservation efforts for A. cervicornis should focus on maintaining and managing populations locally rather than relying on larval inputs from elsewhere.     

Long-term acclimation to elevated pCO2 alters carbon metabolism and reduces growth in the Antarctic diatom Nitzschia lecointei

Increasing atmospheric CO₂ levels are driving changes in the seawater carbonate system, resulting in higher pCO₂ and reduced pH (ocean acidification). Many studies on marine organisms have focused on short-term physiological responses to increased pCO₂, and few on slow-growing polar organisms with a relative low adaptation potential. In order to recognize the consequences of climate change in biological systems, acclimation and adaptation to new environments are crucial to address. In this study, physiological responses to long-term acclimation (194 days, approx. 60 asexual generations) of three pCO₂ levels (280, 390 and 960 µatm) were investigated in the psychrophilic sea ice diatom Nitzschia lecointei. After 147 days, a small reduction in growth was detected at 960 µatm pCO₂. Previous short-term experiments have failed to detect altered growth in N. lecointei at high pCO₂, which illustrates the importance of experimental duration in studies of climate change. In addition, carbon metabolism was significantly affected by the long-term treatments, resulting in higher cellular release of dissolved organic carbon (DOC). In turn, the release of labile organic carbon stimulated bacterial productivity in this system. We conclude that long-term acclimation to ocean acidification is important for N. lecointei and that carbon overconsumption and DOC exudation may increase in a high-CO₂ world.     

Clonal diversity impacts coral cover in Acropora cervicornis thickets: Potential relationships between density,growth, and polymorphisms

As coral reefs decline, cryptic sources of resistance and resilience to stress may be increasingly important for the persistence of these communities. Among these sources, inter‐ and intraspecific diversity remain understudied on coral reefs but extensively impact a variety of traits in other ecosystems. We use a combination of field and sequencing data at two sites in Florida and two in the Dominican Republic to examine clonal diversity and genetic differentiation of high‐ and low‐density aggregations of the threatened coral Acropora cervicornis in the Caribbean. We find that high‐density aggregations called thickets are composed of up to 30 genotypes at a single site, but 47% of genotypes are also found as isolated, discrete colonies outside these aggregations. Genet–ramet ratios are comparable for thickets (0.636) and isolated colonies after rarefaction (0.569), suggesting the composition of each aggregation is not substantially different and highlighting interactions between colonies as a potential influence on structure. There are no differences in growth rate, but a significant positive correlation between genotypic diversity and coral cover, which may be due to the influence of interactions between colonies on survivorship or fragment retention during asexual reproduction. Many polymorphisms distinguish isolated colonies from thickets despite the shared genotypes found here, including putative nonsynonymous mutations that change amino acid sequence in 25 loci. These results highlight intraspecific diversity as a density‐dependent factor that may impact traits important for the structure and function of coral reefs.     

The reproductive seasonality and gametogenic cycle of Acropora cervicornis off Broward County, Florida, USA

Reproductive characters of the Caribbean reef-building coral Acropora cervicornis were investigated based on histological samples collected from April 2001 through October 2002. Oogenesis commenced in early to mid-October through November and spermatogenesis was initiated from January to March. The onset of gametogenesis was staggered, exhibiting up to approximately a 1-month delay within colonies. In the hermaphroditic polyps, the observed male-to-female gonad ratio was nearly 1:1 and ripe oocytes represented over 70% of the total gonadal volume. Fecundity estimates based on Stage IV ova ranged between 10.4 and 21.8 mm³ per square centimeter per year, comparable to A. cervicornis in Puerto Rico and other broadcasting Indo-Pacific Acropora. Fecundity estimates based on Stage III vitellogenic oocytes indicated statistically significant differences among study sites. Spawning in field conditions was observed in 2001, 2003, and 2004 from 2300 to 2330 h. Gamete release generally occurred synchronously between nights two and seven after the full moon of July or August. However in 2003, multiple, small-scale gamete release episodes occurred over more than one lunar cycle. This coincided with the full moon occurring early in the month of July. While prolific gamete production is reported in this study, low levels of recruitment have been reported for this species. Thus, the highly fragmenting A. cervicornis may rely heavily on asexual reproduction for population maintenance and expansion, and recovery after disturbance may be greatly protracted.     

Restricted gene flow in the Caribbean staghorn coral Acropora cervicornis: implications for the recovery of endangered reefs

Coral reef conservation requires information about the distance over which healthy reefs can rescue damaged reefs through input of coral larvae. This information is desperately needed in the Caribbean where the 2 dominant shallow water corals Acropora cervicornis and Acropora palmata have suffered unprecedented declines. Here we compare the population genetic structure in the staghorn coral A. cervicornis across the greater Caribbean using DNA sequence data from 1 mitochondrial and 3 nuclear genes. Data from 160 individuals from 22 populations and 9 regions show that A. cervicornis exhibits significant population genetic structure across the greater Caribbean in both the mitochondrial (Phi(st) = 0.130) and nuclear data (Phi(st) = 0.067). The highest population structure was observed in the species' own, native mtDNA haplotypes (Phi(st) = 0.235). Introgressed alleles from A. palmata tempered higher population structure in A. cervicornis over regional scales but in some cases generated highly localized "introgression hot spots" and fine-scale genetic structure among reefs separated by as few as 2 km. These data show that larval dispersal over moderate or long distances (>500 km) is limited for this threatened species and in some cases locally limited as well. Thus, the endangered Caribbean staghorn corals require local source populations for their recovery and targeted conservation efforts over spatial scales much smaller than the hundreds to thousands of kilometers usually proposed for marine reserves.     

Differential survival of nursery‐reared Acropora cervicornis outplants along the Florida reef tract

In recent decades, the Florida reef tract has lost over 95% of its coral cover. Although isolated coral assemblages persist, coral restoration programs are attempting to recover local coral populations. Listed as threatened under the Endangered Species Act, Acropora cervicornis is the most widely targeted coral species for restoration in Florida. Yet strategies are still maturing to enhance the survival of nursery‐reared outplants of A. cervicornis colonies on natural reefs. This study examined the survival of 22,634 A. cervicornis colonies raised in nurseries along the Florida reef tract and outplanted to six reef habitats in seven geographical subregions between 2012 and 2018. A Cox proportional hazards regression was used within a Bayesian framework to examine the effects of seven variables: (1) coral‐colony size at outplanting, (2) coral‐colony attachment method, (3) genotypic diversity of outplanted A. cervicornis clusters, (4) reef habitat, (5) geographical subregion, (6) latitude, and (7) the year of monitoring. The best models included coral‐colony size at outplanting, reef habitat, geographical subregion, and the year of monitoring. Survival was highest when colonies were larger than 15 cm (total linear extension), when outplanted to back‐reef and fore‐reef habitats, and when outplanted in Biscayne Bay and Broward–Miami subregions, in the higher latitudes of the Florida reef tract. This study points to several variables that influence the survival of outplanted A. cervicornis colonies and highlights a need to refine restoration strategies to help restore their population along the Florida reef tract.     

Larval settlement preferences and post-settlement survival of the threatened Caribbean corals Acropora palmata and A. cervicornis

The settlement specificity of two threatened Caribbean corals, Acropora palmata and A. cervicornis, was tested by measuring their rates of larval metamorphosis in response to crustose coralline algae (CCA) and other substrata. In the no-choice experiments, the coral larvae were placed in six treatments: filtered seawater (FSW), a fragment of biofilmed dead skeleton of A. palmata, or a fragment of one of four species of CCA (Hydrolithon boergesenii, Porolithon pachydermum, Paragoniolithon solubile, and Titanoderma prototypum). Within each CCA treatment, there were three different substrata on which to settle and metamorphose: (1) the CCA surface, (2) the rock under the CCA, or (3) the plastic dish. The 5-day-old larvae of both A. palmata and A. cervicornis had similar rates of total metamorphosis (all substrata combined) in every treatment (excluding FSW) even in the absence of CCA. However, there were differences in larval behavior among the CCA species since the larvae settled and metamorphosed on different substrata in the presence of different CCA species. In the no-choice experiments the larvae of both corals had higher rates of metamorphosis on the top surfaces of H. boergesenii and/or T. prototypum than on P. pachydermum. In the choice experiments, the coral larvae were offered two species of CCA in the same dish. When given a choice, both species of coral larvae had more settlement and metamorphosis on the surface of H. boergesenii or T. prototypum or clean rock than onto the surface of P. solubile. After 6 weeks in the field, transplanted A. palmata recruits had approximately 15% survival on both T. prototypum and H. boergesenii, but A. cervicornis recruits only survived on T. prototypum (13%). Some, but not all, CCA species facilitated the larval settlement and post-settlement survival of these two threatened corals, highlighting the importance of benthic community composition for successful coral recruitment.