Rhian G. Waller

Anthropogenic Impacts on the Corner Rise Seamounts, North-West Atlantic Ocean

Here we report the first direct underwater observations of extensive human-caused impacts on two remote seamounts in the Corner Rise complex (north-western Atlantic). This note documents evidence of anthropogenic damage on the summits of Kukenthal peak (on Corner Seamount) and Yakutat Seamount, likely resulting from a limited Russian fishery from the mid-1970s to the mid-1990s, highlighting how bottom trawling can have long-term detrimental effects on deep-water benthic fauna.

Deep-water Scleractinia (Cnidaria: Anthozoa): current knowledge of reproductive processes

Little is known of the basic biology and ecology of the numerous species of deep-water scleractinians found in all the world’s oceans. Of all the biological processes, reproduction is the most fundamental. Without knowledge of a species’ reproduction, we know little about how they survive both the environment that is the deep-sea, and the increasing anthropogenic effects of man’s exploration for new fisheries and energy reserves.

Cold-water coral distributions in the drake passage area from towed camera observations--initial interpretations.

Seamounts are unique deep-sea features that create habitats thought to have high levels of endemic fauna, productive fisheries and benthic communities vulnerable to anthropogenic impacts. Many seamounts are isolated features, occurring in the high seas, where access is limited and thus biological data scarce. There are numerous seamounts within the Drake Passage (Southern Ocean), yet high winds, frequent storms and strong currents make seafloor sampling particularly difficult. As a result, few attempts to collect biological data have been made, leading to a paucity of information on benthic habitats or fauna in this area, particularly those on primarily hard-bottom seamounts and ridges. During a research cruise in 2008 six locations were examined (two on the Antarctic margin, one on the Shackleton Fracture Zone, and three on seamounts within the Drake Passage), using a towed camera with onboard instruments to measure conductivity, temperature, depth and turbidity. Dominant fauna and bottom type were categorized from 200 randomized photos from each location. Cold-water corals were present in high numbers in habitats both on the Antarctic margin and on the current swept seamounts of the Drake Passage, though the diversity of orders varied. Though the Scleractinia (hard corals) were abundant on the sedimented margin, they were poorly represented in the primarily hard-bottom areas of the central Drake Passage. The two seamount sites and the Shackleton Fracture Zone showed high numbers of stylasterid (lace) and alcyonacean (soft) corals, as well as large numbers of sponges. Though data are preliminary, the geological and environmental variability (particularly in temperature) between sample sites may be influencing cold-water coral biogeography in this region. Each area observed also showed little similarity in faunal diversity with other sites examined for this study within all phyla counted. This manuscript highlights how little is understood of these isolated features, particularly in Polar regions.

Reproductive patterns in two deep-water solitary corals from the north-east Atlantic— Flabellum alabastrum and F. angulare (Cnidaria: Anthozoa: Scleractinia)

Gametogenesis and reproductive periodicity of the solitary scleractinians Flabellum alabastrum (from the Rockall Trough) and F. angulare (from the Porcupine Seabight) were investigated. Samples were collected between depths from 1370 to 2190 m for F. alabastrum and 2412 to 2467 m for F. angulare. Both species showed gonochorism with a 1:1 sex-ratio and broadcast spawning of gametes is inferred from the lack of brooded planulae. Oocyte sizes were large in both species (925 ?m in F. alabastrum and 1015 ?m in F. angulare), suggesting lecithotrophic larval development. Fecundity and periodicity of oocyte development differed between the two species. Flabellum alabastrum produced a maximum of 2800 oocytes per polyp quasi-continuously, whereas the deeper species F. angulare produced a maximum of 550 oocytes per polyp either seasonally or periodically. Both species showed size-dependent fecundity. The data show a decrease in oocyte size and fecundity with depth, in concordance with other deep-water scleractinian species.

Sexual Reproduction and Seasonality of the Alaskan Red Tree Coral, Primnoa pacifica

The red tree coral Primnoa pacifica is an important habitat forming octocoral in North Pacific waters. Given the prominence of this species in shelf and upper slope areas of the Gulf of Alaska where fishing disturbance can be high, it may be able to sustain healthy populations through adaptive reproductive processes. This study was designed to test this hypothesis, examining reproductive mode, seasonality and fecundity in both undamaged and simulated damaged colonies over the course of 16 months using a deepwater-emerged population in Tracy Arm Fjord. Females within the population developed asynchronously, though males showed trends of synchronicity, with production of immature spermatocysts heightened in December/January and maturation of gametes in the fall months. Periodicity of individuals varied from a single year reproductive event to some individuals taking more than the 16 months sampled to produce viable gametes. Multiple stages of gametes occurred in polyps of the same colony during most sampling periods. Mean oocyte size ranged from 50 to 200 µm in any season, and maximum oocyte size (802 µm) suggests a lecithotrophic larva. No brooding larvae were found during this study, though unfertilized oocytes were found adhered to the outside of polyps, where they are presumably fertilized. This species demonstrated size-dependent reproduction, with gametes first forming in colonies over 42-cm length, and steady oocyte sizes being achieved after reaching 80-cm in length. The average fecundity was 86 (±12) total oocytes per polyp, and 17 (±12) potential per polyp fecundity. Sub-lethal injury by removing 21–40% of colony tissue had no significant reproductive response in males or females over the course of this study, except for a corresponding loss in overall colony fecundity. The reproductive patterns and long gamete generation times observed in this study indicate that recruitment events are likely to be highly sporadic in this species increasing its vulnerability to anthropogenic disturbances.

Notes on reproduction of eight species of Eastern Pacific cold-water octocorals

This study examined the reproductive ecology of eight Eastern Pacific deep-sea octocorals, collected from Washington to Southern California. The sexuality, reproductive mode, oocyte size, and fecundity of each species were identified using histological techniques. This research increases the knowledge of basic life histories of deep-sea corals. Swiftia simplex had the highest total fecundity of 42.53 (±9.82 SE) oocytes per polyp. Mean oocyte diameters in S. simplex and S. pacifica females differs among sample months. Swiftia pacifica and S. kofoidi had the lowest total fecundity: 4.6 (±2.06 SE) and 3 (±1.53 SE) oocytes per polyp, respectively.

Sedimentation and the Reproductive Biology of the Hawaiian Reef-Building Coral Montipora capitata

Environmental conditions can influence the physiology of marine organisms and have important implications for their reproductive performance and capacity to supply new recruits. This study examined the seasonal reproductive patterns of the coral Montipora capitata in habitats exposed to different sedimentation regimes. Although M. capitata is a main reef-building coral in the Hawaiian Archipelago, little is known about the gametogenic cycle and reproductive ecology of this important species. Our results indicate that gamete production in M. capitata is a resilient process; no differences in gamete development or fecundity were observed among sites with very different sedimentation regimes. The gametogenic cycle of M. capitata lasts between 10 and 11 months, with spawning occurring over 3–5 months during warmer months (May–September). Oocytes were found throughout the year, but spermatocysts were only found April–August. The largest increases in oocyte size occurred during February to May, the months when solar radiation increased rapidly. The largest variation in oocyte sizes was found during July and August; during this period individual colonies contained mature oocytes for immediate spawning and new oocytes being formed for spawning the next year. The capacity of M. capitata to reproduce in areas with high sedimentation is an interesting finding highlighting the potential of the species for acclimatization, adaptation, or both. Despite this optimistic finding, the management of terrestrial runoff and the restoration of habitat quality for corals remains a top priority to ensure the renewal and maintenance of coral populations.

Octocoral gardens in the Gulf of Maine (NW Atlantic)

Octocorals had been considered a common component of the seafloor fauna in the Gulf of Maine, but it appears a century of impacts have reduced coral distribution to small refugia. Here we provide a preliminary report of a recent expedition that discovered dense coral garden communities at two sites >200 m depth.

Southern ocean corals: Cabo de Hornos

The widespread distribution of cold-water reefs is becoming better documented through deep-sea exploration. Historically, these efforts have focused on the waters of North America and Europe, leaving large gaps in our knowledge of the rest of the deep ocean. Here, we describe spectacular coral growths in the Southern Ocean. A few coral specimens have been collected from the Drake Passage region (Cairns 1982), but it was not until 2008 that an expedition was launched specifically to study cold-water coral distributions in space and time (Burke et al. 2010). During that cruise, we found that corals were abundant across the Drake Passage (Waller et al. 2011) and thus revisited in 2011 with a Drop Camera system to investigate these areas in greater detail. In this Reef Site, we show the first high-resolution images of the diverse coral assemblages on Cabo de Hornos (Cape Horn—57 04S, 67 30W), from 500 m to over 1,400 m depth. Stylasterids dominated this ecosystem, but large numbers of octocorals and solitary corals were also present. Dead stylasterids were observed in the images (e.g., Fig. 1a, b) indicating that reef formation has been active over time. At the deeper locations (Fig. 1c, d), the largest aggregations occurred on boulders and bedrock, though free-living solitary corals (Flabellum sp.) were frequently seen in sediments. In all areas where corals were present, a high diversity of associated fauna was also observed (e.g., sponges, ophiuroids, cephalopods, fish, and actinarians). This area appears to be a hotspot of biodiversity in the deep sea, perhaps representing a key larval source of coldwater corals into the Drake Passage.

Effects of in-vitro pH decrease on the gametogenesis of the red tree coral, Primnoa pacifica

Primnoa pacifica is the most ecologically important coral species in the North Pacific Ocean where it provides important habitat for commercially important fish and invertebrates. Ocean acidification (OA) is more rapidly increasing in high-latitude seas because anthropogenic CO2 uptake is greater in these regions. This is due to the solubility of CO2 in cold water and the reduced buffering capacity due to low alkalinity of colder waters. Primnoa pacifica colonies were cultured for six to nine months in either pH 7.55 (predicted 2100 pH levels) or pH 7.75 (control). Oocyte development and fecundity in females, and spermatocyst stages in males were measured to assess the effects of pH on gametogenesis. Oocyte diameters were 13.6% smaller and fecundities were 30.9% lower in the Year 2100 samples, indicating that OA may limit oocyte formation, potentially through lipid limitation. A higher proportion of vitellogenic oocytes (65%) were also reabsorbed (oosorption) in the Year 2100 treatment. Lowered pH appeared to advance the process of spermatogenesis with a higher percentage of later stage sperm compared to control controls. There was a laboratory effect observed in all measurement types, however these only significantly affected the analyses of spermatogenesis. These results indicate that reproduction may not be possible in an acidified ocean, or that if spawning could occur, spawned oocytes would not be sufficiently equipped to support the normal development of larvae.