J. Anthony Koslow

Diversity and endemism of the benthic seamount fauna in the southwest Pacific.

Seamounts comprise a unique deep-sea environment, characterized by substantially enhanced currents and a fauna that is dominated by suspension feeders, such as corals. The potential importance of these steep-sided undersea mountains, which are generally of volcanic origin, to ocean biogeography and diversity was recognized over 40 years ago, but this environment has remained very poorly explored. A review of seamount biota and biogeography reported a total of 597 invertebrate species recorded from seamounts worldwide since the Challenger expedition of 1872. Most reports, based on a single taxonomic group, were extremely limited: 5 seamounts of the estimated more than 30,000 seamounts in the worlds oceans accounted for 72% of the species recorded. Only 15% of the species occurring on seamounts were considered potential seamount endemics. Here we report the discovery of more than 850 macro- and megafaunal species from seamounts in the Tasman Sea and southeast Coral Sea, of which 29–34% are new to science and potential seamount endemics. Low species overlap between seamounts in different portions of the region indicates that the seamounts in clusters or along ridge systems function as ‘island groups’ or ‘chains,’ leading to highly localized species distributions and apparent speciation between groups or ridge systems that is exceptional for the deep sea. These results have substantial implications for the conservation of this fauna, which is threatened by fishing activity.

A Call for Deep-Ocean Stewardship

The precautionary approach and collaborative governance must balance deep-ocean use and protection. Covering more than half the planet, the deep ocean sequesters atmospheric CO2 and recycles major nutrients; is predicted to hold millions of yet-to-be-described species; and stores mind-boggling quantities of untapped energy resources, precious metals, and minerals (1). It is an immense, remote biome, critical to the health of the planet and human well-being. The deep ocean (defined here as below a typical continental shelf break, >200 m) faces mounting challenges as technological advances—including robotics, imaging, and structural engineering—greatly improve access. We recommend a move from a frontier mentality of exploitation and single-sector management to a precautionary system that balances use of living marine resources, energy, and minerals from the deep ocean with maintenance of a productive and healthy marine environment, while improving knowledge and collaboration.

Is there a decline in marine phytoplankton

Arising from D. G. Boyce, M. R. Lewis & B. Worm 466, 591–596 (2010)10.1038/nature09268; Boyce et al. replyPhytoplankton account for approximately 50% of global primary production, form the trophic base of nearly all marine ecosystems, are fundamental in trophic energy transfer and have key roles in climate regulation, carbon sequestration and oxygen production. Boyce et al. compiled a chlorophyll index by combining in situ chlorophyll and Secchi disk depth measurements that spanned a more than 100-year time period and showed a decrease in marine phytoplankton biomass of approximately 1% of the global median per year over the past century. Eight decades of data on phytoplankton biomass collected in the North Atlantic by the Continuous Plankton Recorder (CPR) survey, however, show an increase in an index of chlorophyll (Phytoplankton Colour Index) in both the Northeast and Northwest Atlantic basins (Fig. 1), and other long-term time series, including the Hawaii Ocean Time-series (HOT), the Bermuda Atlantic Time Series (BATS) and the California Cooperative Oceanic Fisheries Investigations (CalCOFI) also indicate increased phytoplankton biomass over the last 20–50 years. These findings, which were not discussed by Boyce et al., are not in accordance with their conclusions and illustrate the importance of using consistent observations when estimating long-term trends.

Multi-decadal oceanic ecological datasets and their application in marine policy and management

Long-term biological time-series in the oceans are relatively rare. Using the two longest of these we show how the information value of such ecological time-series increases through space and time in terms of their potential policy value. We also explore the co-evolution of these oceanic biological time-series with changing marine management drivers. Lessons learnt from reviewing these sequences of observations provide valuable context for the continuation of existing time-series and perspective for the initiation of new time-series in response to rapid global change. Concluding sections call for a more integrated approach to marine observation systems and highlight the future role of ocean observations in adaptive marine management.

Oceanic evidence of climate change in southern Australia over the last three centuries

Chemical analysis of deepwater octocorals collected at 1000 m depth off southern Australia indicates long-term cooling, beginning in the mid-18th century. This cooling appears to reflect shoaling of isotherms along the continental shelf, that can be related statistically, observationally and by modeling to increasing coastal sea-surface temperatures, that in turn reflect a poleward extension of the SW Pacific boundary current (the East Australian Current). The oceanographic changes implied by the coral record suggest climate change in temperate Australia starting about the time of European settlement. Correlations between temperate Australian and Antarctic indices suggest these long-term changes might also be relevant to Antarctic climate.

The mid-slope demersal fish community off southeastern Australia

Abstract The mid-slope (800–1200 m) demersal fish community off southeastern Australia was sampled at 376 random, depth-stratified trawl stations. The mean density of demersal species was 4.82 g m −2 . Thirty-seven families and 111 species of demersal fish were represented in the catch. The density of mid-slope fishes off southeastern Australia was comparable to that observed in the Northern Hemisphere. However, landings and acoustic and egg surveys of orange roughy ( Hoplostethus atlanticus ) indicate that densities of that species alone are an order of magnitude higher than the total fish density indicated by trawl surveys. Water-column productivity over the mid-slope region appears insufficient to support the higher range of density estimates, implying a significant flux of energy into the region either from offshore or downslope. The dominant mid-slope demersal fishes appear to comprise an identifiable community within a biogeographic province that extends at least from the Great Australian Bight to the Chatham Rise (New Zealand), a distance of ∼5000 km. Distinct assemblages of demersal fish were found at upper (500 m) and mid-slope (800–1200 m) depths off southeast Australia. The mid-slope community could be sub-divided into assemblages by depth (shallow, intermediate and deep) and area (east and west Tasmania), which were statistically robust although with considerable overlap of species composition. There was no overlap in species composition of the southeast Australian mid-slope demersal fish community with fish communities at similar latitudes and depths in the North Pacific, but there were affinities with those in the North Atlantic. These biogeographic patterns, which appear consistent with oceanic circulation at intermediate depths, provide strong evidence that negates the recent hypothesis that deepwater fish communities cannot be defined over broad areas and are only random assemblages ( Haedrich and Merrett , 1990, Progress in Oceanography , 24 , 239–250).

Community structure in North Atlantic deep-sea fishes

Abstract Haedrich and Merrett (1988, 1990) assembled the catch data on demersal fishes from 9 deep-sea trawl surveys around the rim of the North Atlantic and concluded that species distributions were generally not coherent beyond the local scale and the composition of species assemblages appeared random. However, their conclusions were based in part upon using strata that were inadequately sampled (i.e. strata based on ≤ 10 samples and about 100 individuals) and upon the use of similarity coefficients that were biassed by large differences in sample size among strata. Classification and ordination analyses of the better-sampled strata indicated patterns in the distribution of species in three principal dimensions: depth, latitude, and amphi-oceanically. The distribution of many species overlapped adjacent climatic zones. Shallower-living (upper and mid-slope) species tended to be restricted to only one side of the Atlantic, whereas many deeper-living species occurred on both sides of the ocean. Species occurring on the two sides of the Atlantic tended to be either temperate-boreal species, whose distribution spanned the northern rim of the ocean, or tropical/subtropical species distributed across low latitudes. The distribution of deepwater fishes is shown to be consistent with the salient features of circulation and water mass structure in the North Atlantic.

Avoidance of a camera system by a deepwater fish, the orange roughy (Hoplostethus atlanticus)

Abstract The response of the benthopelagic fish, orange roughy ( Hoplostethus atlanticus ), to lowering an underwater camera was monitored acoustically. Acoustic layers of the fish at 660–790 m depth dispersed rapidly at least 30–40 m when the camera was ∼130 m above them. The reaction occurred day and night and prior to activation of the strobe lights, so it was presumably mediated by the low-frequency sound of the system being lowered rather than visually. Orange roughy contain a pronounced lateral line and extensive frontal sensory canal system that may be used to sense low-frequency sound. Our observations indicate that some marine species are highly sensitive even to non-capture sampling gears, so use of non-remote methods of sampling may lead to highly biased estimates of density. The avoidance response is consistent with the relatively high metabolic levels that have been reported for this species, as well as with their very low estimated rates of natural mortality. We speculate that the response has evolved to facilitate escape from large, highly mobile predators.

Occurrence of High Levels of Tetracosahexaenoic Acid in the Jellyfish Aurelia sp

The FA composition of the pelagic jellyfish Aurelia sp. collected from off-shore Western Australia waters was determined by capillary GC and GC-MS, with confirmation of PUFA structure performed by analysis of 4,4-dimethyloxazoline derivatives. PUFA constituted 47.6% of the total FA, with the essential PUFA eicosapentaenoic acid (FPA), arachidonic acid, and DHA accounting for 34%. Of particular interest, the unusual very long chain PUFA 6,9,12,15,18,21-tetracosahexaenoic acid (THA, 24∶6n−3) was present at 9.3%, and the rarely reported 6,9,12,15,18-tetracosapentaenoic acid (24∶5n−6) also was detected at 0.8%. To our knowledge, this represents the first report of THA as a major PUFA in a pelagic marine organism.

Resilience and stability of a pelagic marine ecosystem

The accelerating loss of biodiversity and ecosystem services worldwide has accentuated a long-standing debate on the role of diversity in stabilizing ecological communities and has given rise to a field of research on biodiversity and ecosystem functioning (BEF). Although broad consensus has been reached regarding the positive BEF relationship, a number of important challenges remain unanswered. These primarily concern the underlying mechanisms by which diversity increases resilience and community stability, particularly the relative importance of statistical averaging and functional complementarity. Our understanding of these mechanisms relies heavily on theoretical and experimental studies, yet the degree to which theory adequately explains the dynamics and stability of natural ecosystems is largely unknown, especially in marine ecosystems. Using modelling and a unique 60-year dataset covering multiple trophic levels, we show that the pronounced multi-decadal variability of the Southern California Current System (SCCS) does not represent fundamental changes in ecosystem functioning, but a linear response to key environmental drivers channelled through bottom-up and physical control. Furthermore, we show strong temporal asynchrony between key species or functional groups within multiple trophic levels caused by opposite responses to these drivers. We argue that functional complementarity is the primary mechanism reducing community variability and promoting resilience and stability in the SCCS.