High potential for formation and persistence of chimeras following aggregated larval settlement in the broadcast spawning coral, Acropora millepora

In sessile modular marine invertebrates, chimeras can originate from fusions of closely settling larvae or of colonies that come into contact through growth or movement. While it has been shown that juveniles of brooding corals fuse under experimental conditions, chimera formation in broadcast spawning corals, the most abundant group of reef corals, has not been examined. This study explores the capacity of the broadcast spawning coral Acropora millepora to form chimeras under experimental conditions and to persist as chimeras in the field. Under experimental conditions, 1.5-fold more larvae settled in aggregations than solitarily, and analyses of nine microsatellite loci revealed that 50 per cent of juveniles tested harboured different genotypes within the same colony. Significantly, some chimeric colonies persisted for 23 months post-settlement, when the study ended. Genotypes within persisting chimeric colonies all showed a high level of relatedness, whereas rejecting colonies displayed variable levels of relatedness. The nearly threefold greater sizes of chimeras compared with solitary juveniles, from settlement through to at least three months, suggest that chimerism is likely to be an important strategy for maximizing survival of vulnerable early life-history stages of corals, although longer-term studies are required to more fully explore the potential benefits of chimerism.     

Transportation techniques for massive scleractinian corals

Transportation techniques for scleractinian corals have been described mainly for fragments and small colonies. As part of a recent study on captive sexual reproduction of the Caribbean species Montastrea annularis and Diploria strigosa, we transported relatively large (max. diameter of 21 cm), heavy (max. weight of 9,200 g) colonies of both species from Curaçao, Netherlands Antilles, to Rotterdam, The Netherlands. A new transportation technology was applied whereby the corals were transplanted to specially designed PVC crosses to provide stabilization during transport. In two transports (November 2001 and February 2002), 100 colonies were transported submerged, in a shipping time of >35 hr. The survival rate measured 2 weeks after transport was 100%. Four and 8 months after transport, respectively, two colonies of D. strigosa died without any obvious cause. In November 2002 we observed an outbreak of Dark Spots disease (DSD) affecting two‐thirds of the colonies of M. annularis. Although the colonies did not show any symptoms when they were collected, the disease most probably was transferred when the coral were transported from the field to the laboratory. The presented method is appropriate for transporting large, heavy corals–especially for scientific purposes. In general, species‐specific properties, colony size, and transportation time determine which transportation method should be applied. In the future, there may be a shift toward transports of fragments, coral larvae, and primary polyps to reduce collections in the field. Zoo Biol 23:165–176, 2004. © 2004 Wiley‐Liss, Inc.     

Chemical signals in gametogenesis, spawning, and larval settlement and defense of the soft coral Sinularia polydactyla

 Mass spawning strategies of hard and soft corals on the Great Barrier Reef, Australia have been described in recent years. Nonetheless, the applicability of those studies to corals on other reef systems has not been well documented. Here we describe the mass spawning behavior of the soft coral Sinularia polydactyla on coral reefs surrounding Guam; specifically we describe the events in an annual gametogenic cycle including steroidogenesis, spawning, settlement and early life history defense. The gametogenic cycle of female colonies lasted 12 months while male colonies produced viable sperm within 9 months. Sinularia polydactyla exhibited a split spawn between March and June that correlated with a significant reduction in tissue concentrations of progesterone and testosterone. Estradiol was released into the water column, apparently by female colonies, just prior to spawning. There was a trend for preferential larval settlement in the presence of the crustose coralline algae Hydrolithon reinboldii rather than coral rubble, a natural biofilm, or filtered seawater. The defensive compounds pukalide and 11β-acetoxypukalide were found in eggs and larvae at adult level and three-fold lower than adult-level concentrations, respectively. These compounds provided some predator deterrent and antimicrobial protection against an ecologically relevant omnivorous fish Canthigaster solandri and a sympatric microbe Vibrio sp. Accepted: 10 September 1998     

The dynamics of the restoration of mechanical damage to colonies of the scleractinian coral Porites lutea under conditions of competition with algal settlers for substratum

Natural and anthropogenic catastrophes in the last decades of the 20th century and at the beginning of the new century have evoked significant changes in the biological diversity of coral reefs, viz., the mortality of hermatypic scleractinian corals that are replaced by communities of marine algae and seaweeds. In this connection, the study of the dynamics of algal colonization of a newly formed substratum and competition for the substratum between hermatypic corals and algae is of topical interest. This paper describes the results of investigations conducted in 2003 at the Sesoko Marine Biological Station of Ryukyu University (Okinawa, Japan). Colonies of the massive scleractinian coral Porites lutea were sampled from a fringing reef of Sesoko Island. Damages were inflicted on the upper portions of the colonies, the damaged coral fragments were placed in aquaria and maintained for six months under different light intensities in the absence of herbivorous and corallivorous animals. The experiments showed that under bright (70–90% of incident photosynthetically active radiation, PAR₀) and under moderate light (20–30% of PAR₀), the damaged parts of colonies of about 25 cm² were overgrown by newly formed polyps within six months. Under dim light (2–5% of PAR₀), this period was not sufficient for recovery from lesions. During the first month, the recovery rate of colonies was the highest and depended on the physiological state of the corals and light intensity: in bright and moderate light it was two times and more higher than under low light. During the subsequent months, the recovery rate was significantly lower and depended mainly on the degree of overgrowth of dead portions with algae and on their species composition. Under bright and moderate light, algal colonization of damaged colonies started with the settling of colonial and filamentous diatoms, cyanobacteria and green algae, followed by the formation of the algal turf community. Communities of red calcareous crusts and fleshy algae were mainly formed on damaged corals under low light. A comparison of experimental results showed that damaged colonies maintained in aquaria in the absence of herbivorous and corallivorous animals recovered 1.5 times faster than in the sea. We hypothesize that herbivorous fish have a negative rather than positive influence on the recovery of damaged colonies.     

Miocene intertidal zonation on a volcanically active shoreline: Porto Santo in the Madeira Archipelago,Portugal

Santos, A., Mayoral, E.J., da Silva, C.M., Cachão, M., Johnson, M.E. & Baarli, B.G. Miocene intertidal zonation on a volcanically active shoreline: Porto Santo in the Madeira Archipelago, Portugal. Lethaia, Vol. 44, pp. 26–32. Short‐term biological colonization of rockgrounds on the basaltic shorelines of oceanic islands has, as yet, been poorly explored. A Miocene sea cliff on Ilhéu de Cima off Porto Santo in the Madeira Archipelago of Portugal provides a case study showing intertidal zonation with two types of barnacles, serpulid worm tubes, two coral species, epifaunal bivalves and the trace fossils of endolithic bivalves. Large barnacles (Balanus sp.) and serpulids are limited to the upper 400 mm of a basalt cliff of 1.6 m in height. Small barnacles, possibly of the same species, extend to the base. The upper half includes the corals Isophyllastrea orbignyana and Tarbellastraea reussiana, to which many small, coral‐inhabiting, barnacles (Ceratoconcha costata) are fixed. Borings identified as Gastrochaenolites torpedo appear through the bottom two‐thirds of the cliff face. Rarely, Gastrochaenolites lapidicus is exposed in longitudinal section with borings up to 45 mm deep in solid basalt. Epifaunal bivalves, such as Spondylus sp., are limited to a middle zone. Associated with the sea cliff is an outer platform on which a multitude of T. reussiana colonies occur in growth position. The corals exhibit planar erosion over180 m². The shelf was faulted and cut by a basalt dike prior to the brief recolonization of I. orbignyana, found attached to low fault scarps. Habitation of the sea cliff was facilitated by rising sea level, but abruptly terminated by burial under volcanoclastic ejecta. □Basalt bioerosion, coastal dynamics, Ilhéu de Cima (Porto Santo), Miocene intertidal zonation, volcanogenic perturbations.     

Feasibility of early outplanting of sexually propagated Acropora verweyi for coral reef restoration demonstrated in the Philippines

Over the last 20 years, coral sexual propagation techniques for reef restoration have been steadily developed and improved. However, these techniques involve considerable time and costs to grow coral propagules. There is a need to examine the optimal size of juvenile corals for outplantation. Here, we outplanted sexually propagated small (3–5 mm diameter) and large (10–15 mm diameter) Acropora verweyi corals at 4 months after fertilization at two sites in northwestern Philippines, and compared their survival and radial growth rate after a year. A. verweyi coral juveniles (n = 240) exhibited an overall mean survival of 29.5% and growth rate of 11.12 ± 6.2 mm/year (mean ± SD). Large colonies had a significantly higher growth rate than smaller colonies. Although survivorship of large juveniles was significantly better than that of the smaller ones at one site, it did not differ significantly at the other. Each 4‐month‐old coral cost US$1.52 to produce, while the cost of each of the outplanted juveniles (n = 240) was about US$2.67, whereas the cost of each survivor about a year after outplantation was US$11.47. Results suggest that A. verweyi reared in ex situ nurseries for only 4 months can survive reasonably well when outplanted onto coral reefs.     

Sexual reproduction of Hawaiian black corals,with a review of the reproduction of antipatharians (Cnidaria: Anthozoa: Hexacorallia)

Abstract. Black corals (Cnidaria: Antipatharia) are ecologically important members of the sessile invertebrate fauna, but due to their typical deep‐water environments (>50 m), very little is known about their basic biology, including reproduction. We used histological techniques to examine the sexual reproduction of members of eight species of antipatharians collected from the Hawaiian Islands over a wide depth range (10–1327 m). Gametes of all species examined were found in association with the primary transverse mesenteries, which in some cases reached into the cavity of lateral tentacles. Specimens contained either spermatocysts or oocytes, but never both within the same individual, suggesting either a gonochoric or a sequentially hermaphroditic mode of reproduction. No developing embryos or larvae were observed in any of the samples, indicating that fertilization and larval development likely occur externally in the water column and not internally within polyps. We compared our results with previously published information on the sexual reproduction of antipatharians. Our review suggests that in antipatharians, more generally, (1) entire colonies are either female or male (although sequential hermaphroditism cannot be ruled out in most cases and has been reported previously for one species), (2) gametes are confined to the primary transverse mesenteries in most species, and (3) there is no evidence of internal fertilization. Further studies are needed to determine whether gonochorism or sequential hermaphroditism is more prevalent within the Antipatharia, whether dimorphic polyps occur within this taxonomic order, and to examine the reproductive seasonality and larval behavior of individual species.     

A comparison of fatty acid,cholesterol and vitamin composition in sea bass [Dicentrarchus labrax (Linnaeus, 1758)] and sea bream [Sparus aurata (Linnaeus, 1758)] from three cage farm areas: Antalya and Muğla (Turkey) and İskele (Northern Cyprus)

In the present study the fatty acids, cholesterol and vitamin composition in farmed sea bass (8 fish per species per farm; weight range: 389.6–395.8 g, total length range: 297–316 mm) and sea bream (8 fish per species per farm; weight range: 386.8–391.7 g, total length range: 263–268 mm) from three cage farms (?skele in northern Cyprus, Antalya and Mu?la in Turkey) were compared during the harvesting period in June–July 2011. The results showed that the muscles of D. labrax and S. aurata farmed fish were rich in n‐3 fatty acids, but with important differences. For example, the muscles of sea bass farmed in ?skele were rich in docosahexaenoic acid (DHA) and n‐3 polyunsaturated fatty acids (PUFA). Palmitic acid (C16:0) was the primary saturated fatty acid, and oleic acid (C18:1 n‐9) the primary monounsaturated fatty acid in the muscle and liver samples of the cage‐farmed sea bass and sea bream. There were no significant differences in the cholesterol content in the muscles of sea bream farmed in ?skele, Antalya or Mu?la. In conclusion, the n‐3/n‐6 ratio in the muscle of farmed S. aurata and D. labrax is within the recommended limits for a healthy human diet, being very suitable for human nutrition.     

Within-colony feeding selectivity by a corallivorous reef fish: foraging to maximize reward?

Foraging theory predicts that individuals should choose a prey that maximizes energy rewards relative to the energy expended to access, capture, and consume the prey. However, the relative roles of differences in the nutritive value of foods and costs associated with differences in prey accessibility are not always clear. Coral‐feeding fishes are known to be highly selective feeders on particular coral genera or species and even different parts of individual coral colonies. The absence of strong correlations between the nutritional value of corals and prey preferences suggests other factors such as polyp accessibility may be important. Here, we investigated within‐colony feeding selectivity by the corallivorous filefish, Oxymonacanthus longirostris, and if prey accessibility determines foraging patterns. After confirming that this fish primarily feeds on coral polyps, we examined whether fish show a preference for different parts of a common branching coral, Acropora nobilis, both in the field and in the laboratory experiments with simulated corals. We then experimentally tested whether nonuniform patterns of feeding on preferred coral species reflect structural differences between polyps. We found that O. longirostris exhibits nonuniform patterns of foraging in the field, selectively feeding midway along branches. On simulated corals, fish replicated this pattern when food accessibility was equal along the branch. However, when food access varied, fish consistently modified their foraging behavior, preferring to feed where food was most accessible. When foraging patterns were compared with coral morphology, fish preferred larger polyps and less skeletal protection. Our results highlight that patterns of interspecific and intraspecific selectivity can reflect coral morphology, with fish preferring corals or parts of coral colonies with structural characteristics that increase prey accessibility.     

Enhancing coral larval supply and seedling production using a special bundle collection system “coral larval cradle” for large‐scale coral restoration

Larval recruitment is essential for sustaining coral communities and a fundamental tool in some interventions for reef restoration. To improve larval supply and post‐settlement survival in sexually assisted coral restoration efforts, an integrated in situ collector system, the larval cradle, was designed to collect spawned gametes then culture the resulting larvae until settled on artificial substrates. The final design of the larval cradle was cylindrical, a nylon mesh structure with a volume of 9 m³, suspended in the sea and extending vertically toward the seabed. We found three key design features that improved the efficiency of the apparatus: (1) an open area of sea surface and mesh size of less than 100 μm produced high fertilization and optimal survival (>90%), (2) a special skirt‐shaped net (3 m in diameter) with a connection hose for attaching the cradle to collect bundles from many adult colonies over a wide area and at various depths, and (3) adding short square tube pieces, called square hollow sections, as a substrate for enhancing larval settlement and survival, to a larval cradle at 4 days after spawning was optimal for uniform settlement. This system allowed not only the collection of several million eggs, but also subsequent production of several thousand settled juvenile corals, without land facilities. Our design achieved several hundred times higher survival for early life stages of Acropora tenuis compared to nature.     

Bommies away! Logistics and early effects of repositioning 400 tonnes of displaced coral colonies following cyclone impacts on the Great Barrier Reef

For over 40 years, management of the Great Barrier Reef Marine Park (GBRMP) in Australia has focused on limiting human‐use impacts to facilitate natural resilience and recovery. Compounding acute disturbances and chronic stressors have resulted in degradation of coral reef habitats in many areas of the Marine Park. Given current trends and predictions of escalating climate‐driven disturbances, it is increasingly evident that effective management of the GBRMP requires adaptive and novel approaches to protect and restore coral reef health. Here, we provide an overview of the logistical requirements and early‐stage ecological benefits of repositioning 400 tonnes of moderately sized (1–3 m diameter) Porites spp. coral colonies (bommies) that were displaced by cyclone‐generated swells that impacted reefs in the Whitsunday Islands during March 2017. An ecological survey conducted 16 months after the bommie repositioning revealed that several genera of hard coral had settled onto the bommies and that a range of reef fish species were associating with the restored habitat. Early findings suggest that the repositioning of the displaced bommies has assisted in restoring reef habitat structure and settlement habitat for juvenile corals, while improving natural aesthetics, vessel access and tourist experiences at Manta Ray Bay.     

Reproductive features and gonad development cycle of the soft bottom-gravel gorgonian Leptogorgia sarmentosa (Esper, 1791) in the NW Mediterranean Sea

Abstract

Leptogorgia sarmentosa (Cnidaria: Octocorallia) is a common soft bottom-gravel gorgonian in the northwestern Mediterranean Sea. This study examined the annual reproductive cycle of a L. sarmentosa. population at a depth of 30 m, and further determined the sex ratio, the intra-colonial gonadal output variability and the age at first reproduction. L. sarmentosa was gonochoric and the population studied was characterized by a sex ratio slightly biased towards female colonies (1 male:1.6 female). Secondary branches had higher polyp fertility (number of gonads per polyp) compared to primary branches, but because of the number of polyps on the former, most of the sexual effort was actually contributed by the primary branches, as in other gorgonian species. Male colonies became fertile above a height of 21 cm, but female colonies had gonads even in the 1–10 cm height class. Spawning occurred between late August and early September, although there was no direct observation of broadcast spawning or surface brooder strategy. The maximum gonad size was 550 μm in males and 500 μm in females, with a mean diameter of 270 μm for spermaries, and 190 μm for eggs. The number of gonads per polyp prior to spawning reached 4–5 spermaries polyp!1 in male colonies, and 3–4 eggs polyp!1 in female colonies. Spawning did not appear to be synchronized with the full moon. L. sarmentosa appeared to have a different reproductive strategy to other Mediterranean gorgonians (living on hard bottom substrata), probably because of its different habitat preferences and biological (morphology, diet, prey capture rates, growth, biochemical levels) features.     

Reproduction,development, growth,and the length of larval life of Phascolosoma turnerae,a wood‐dwelling deep‐sea sipunculan

Specimens of the deep‐sea sipunculan Phascolosoma turnerae were retrieved over a 5‐year period from fibrous collectors placed for various time intervals at a depth of 520 m in the Tongue of the Ocean, Bahamas. Sipunculans removed from the collectors were counted, weighed, and maintained in the laboratory at 14°C, where they were monitored for gametogenic activity, spawning, development, and growth. In a 2‐year study of seasonality, worms were most abundant in collectors retrieved in the spring and summer, and least abundant in the fall. Small animals (<0.01 g) were present in all seasons and represented ≥70% of the animals in winter collections. Large specimens (>0.16 g) were found from May through August, but in markedly lower frequencies than small animals. Over the entire study, spawning was observed in the laboratory from April through August. We inferred from analyses of size frequencies, growth, and spawning seasonality that settlement of the larvae occurs primarily from November through April and that oceanic larval life could be as short as 7 months and as long as 12–14 months. Cleavage of fertilized eggs, as observed from laboratory spawnings, was spiral and holoblastic, resulting in a trochophore that transformed into a typical planktotrophic pelagosphera larva at 21 d. A few larvae survived as long as 2 months in the laboratory. This is the first study of biological processes in living sipunculans from the deep sea, and one of the first studies of living deep‐sea wood dwellers.     

Effects of juvenile coral-feeding butterflyfishes on host corals

Corals provide critical settlement habitat for a wide range of coral reef fishes, particularly corallivorous butterflyfishes, which not only settle directly into live corals but also use this coral as an exclusive food source. This study examines the consequences of chronic predation by juvenile coral-feeding butterflyfishes on their specific host corals. Juvenile butterflyfishes had high levels of site fidelity for host corals with 88% (38/43) of small (<30 mm) juveniles of Chaetodon plebeius feeding exclusively from a single host colony. This highly concentrated predation had negative effects on the condition of these colonies, with tissue biomass declining with increasing predation intensity. Declines were consistent across both field observations and a controlled experiment. Coral tissue biomass declined by 26.7, 44.5 and 53.4% in low, medium and high predation intensity treatments. Similarly, a 41.7% difference in coral tissue biomass was observed between colonies that were naturally inhabited by juvenile butterflyfish compared to uninhabited control colonies. Total lipid content of host corals declined by 29–38% across all treatments including controls and was not related to predation intensity; rather, this decline coincided with the mass spawning of corals and the loss of lipid-rich eggs. Although the speed at which lost coral tissue is regenerated and the long-term consequences for growth and reproduction remain unknown, our findings indicate that predation by juvenile butterflyfishes represents a chronic stress to these coral colonies and will have negative energetic consequences for the corals used as settlement habitat.     

Metamorphosis and acquisition of symbiotic algae in planula larvae and primary polyps of Acropora spp.

Coral planulae settle, then metamorphose and form polyps. This study examined the morphological process of metamorphosis from planulae into primary polyps in the scleractinian corals Acropora nobilis and Acropora microphthalma, using the cnidarian neuropeptide Hym-248. These two species release eggs that do not contain Symbiodinium. The mode of acquisition of freshly isolated Symbiodinium (zooxanthellae) (FIZ) by the non-symbiotic polyp was also examined. Non-Hym-248 treated swimming Acropora planulae did not develop blastopore, mesenteries or coelenteron until the induction of metamorphosis 16 days after fertilization. The oral pore was formed by invagination of the epidermal layer after formation of the coelenteron in metamorphosing polyps. At 3 days after settlement and metamorphosis, primary polyps exposed to FIZ established symbioses with the Symbiodinium. Two–four days after exposure to FIZ, the distribution of Symbiodinium was limited to the gastrodermis of the pharynx and basal part of the polyps. Eight–ten days after exposure to FIZ, Symbiodinium were present in gastrodermal cells throughout the polyps.     

A Novel Method for Coral Explant Culture and Micropropagation

We describe here a method for the micropropagation of coral that creates progeny from tissue explants derived from a single polyp or colonial corals. Coral tissue explants of various sizes (0.5?C2.5?mm in diameter) were manually microdissected from the solitary coral Fungia granulosa. Explants could be maintained in an undeveloped state or induced to develop into polyps by manipulating environmental parameters such as light and temperature regimes, as well as substrate type. Fully developed polyps were able to be maintained for a long-term in a closed sea water system. Further, we demonstrate that mature explants are also amenable to this technique with the micropropagation of second-generation explants and their development into mature polyps. We thereby experimentally have established coral clonal lines that maintain their ability to differentiate without the need for chemical induction or genetic manipulation. The versatility of this method is also demonstrated through its application to two other coral species, the colonial corals Oculina patigonica and Favia favus.     

Assessing between-colony oxygen isotope variability in the coral Porites lobata at Clipperton Atoll

The eastern Pacific warm tongue is a region of stable and elevated sea surface temperature (SST) located just north of the equator in the eastern Pacific. This warm water mass is thought to influence the position of the Intertropical Convergence Zone (ITCZ) in the eastern Pacific and to directly influence climate in Central America. To assess the use of corals in the development of paleoclimatic reconstructions in this region, we have developed oxygen isotope (δ¹⁸O) time-series from multiple specimens of the massive coral Porites lobata collected at Clipperton Atoll (10°18′N, 109°13′ W). Six near-monthly δ¹⁸O records from different sized (age) colonies where produced for the interval 1986–1994, and three of these were extended back to 1969. All corals sampled were found to contain numerous fish-grazing skeletal scars (～0.5?mm deep scallop shaped hiatuses). Samples collected at 1?mm intervals showed anomalous ¹⁸O/¹⁶O in the area of a bite scar, with 2 to 2.5?mm sampling intervals (10–12/year) minimizing these effects. Our results show that the average δ¹⁸O disequilibrium offset (vital effect) from equilibrium seawater composition for individual corals can vary by up to 0.4‰. However all δ¹⁸O results suggest that the vital effect offset is constant over time. Similar “offsets” are observed in the tops of old (age=～100?y) and young (age=～10?y) colonies, further suggesting that the biologically mediated vital effect offset does not change as a Porites colony ages. A 6-coral average composite δ¹⁸O record was constructed from 1985–1994 and a 3-coral average δ¹⁸O_anomaly record was constructed from 1969–1994. Regression analysis between monthly SST and the 6 coral average δ¹⁸O records yields an r ² correlation of 0.54 (individual r ²-values ranged from 0.27–0.55). The 3 coral δ¹⁸O_anomaly average record has an even lower correlation to SST, with an r ² of 0.40. Potential causes of the only moderate correlation to SST are explored and we find that inferred salinity effects, fish grazing scars, and slight chronology imperfections have all contributed to a reduced correlation to SST. Nevertheless, all El Niño events in this time period appear to be recorded by coral skeletal δ¹⁸O.     

Bacterial community shifts in taxa and diversity in response to localized organic loading in the deep sea

The deep sea is a unique and extreme environment characterized by low concentrations of highly recalcitrant carbon. As a consequence, large organic inputs have potential to cause significant perturbation. To assess the impact of organic enrichment on deep sea microbial communities, we investigated bacterial diversity in sediments underlying two whale falls at 1820 and 2893 m depth in Monterey Canyon, as compared with surrounding reference sediment 10–20 m away. Bacteroidetes, Epsilonproteobacteria and Firmicutes were recovered primarily from whale fall‐associated sediments, while Gammaproteobacteria and Planctomycetes were found primarily within reference sediments. Abundant Deltaproteobacteria were recovered from both sediment types, but the Desulfobacteraceae and Desulfobulbaceae families were observed primarily beneath the whale falls. UniFrac analysis revealed that bacterial communities from the two whale falls (～30 km apart) clustered to the exclusion of corresponding reference sediment communities, suggesting that deposition of whale fall biomass is more influential on deep sea microbial communities than specific seafloor location. The bacterial population at whale‐1820 at 7 months post deposition was less diverse than reference sediments, with Delta‐ and Epsilonproteobacteria and Bacteroidetes making up 89% of the community. At 70 months, bacterial diversity in reference sediments near whale‐2893 had decreased as well. Over this time, there was a convergence of each community's membership at the phyla level, although lower‐taxonomic‐level composition remained distinct. Long‐term impact of organic carbon loading from the whale falls was also evident by elevated total organic carbon and enhanced proteolytic activity for at least 17–70 months. The response of the sedimentary microbial community to large pulses of organic carbon is complex, likely affected by increased animal bioturbation, and may be sustained over time periods that span years to perhaps even decades.     

Reef-Building Corals—Symbiotic Autotrophic Organisms: 2. Pathways and Mechanisms of Adaptation to Light

Ways, mechanisms, and responses of ontogenetic adaptation of reef-building corals to light are discussed on the basis of original and literature data. The possible ways of photoacclimation of corals within the range of tolerance to light are shown: (1) adaptation to bright light (>70% incident photosynthetic active radiation, PAR_s), (2) adaptation to moderate shade (50–10% PAR_s), and (3) adaptation to extremely low light (<5% PAR_s). In each of the ways, general and specific mechanisms and reactions are involved in photoacclimation of corals. Adaptive changes take place in plant (zooxanthellae) and animal (polyps) components of the symbiotic organism. They involve morphology, physiology, and biochemistry of colonial polyps and their zooxanthellae. During changes of the light regime, some adaptive reactions last several months and others occur within a few days. Some physiological and biochemical alterations occur as early as the next day after the light regime changes. The wide range of light tolerance of corals and a great number of mechanisms and reactions of photoacclimation allowing corals to adapt to bright and low light with minimum losses in their metabolic activity give grounds to classify them as a single ecological group of light- and shade-tolerant organisms.