Evidence for seasonal cycles in deep-sea fish abundances: A great migration in the deep SE Atlantic?

Animal migrations are of global ecological significance, providing mechanisms for the transport of nutrients and energy between distant locations. In much of the deep sea (>200 m water depth), the export of nutrients from the surface ocean provides a crucial but seasonally variable energy source to seafloor ecosystems. Seasonal faunal migrations have been hypothesized to occur on the deep seafloor as a result, but have not been documented.

A framework for the development of a global standardised marine taxon reference image database (SMarTaR-ID) to support image-based analyses.

Video and image data are regularly used in the field of benthic ecology to document biodiversity. However, their use is subject to a number of challenges, principally the identification of taxa within the images without associated physical specimens. The challenge of applying traditional taxonomic keys to the identification of fauna from images has led to the development of personal, group, or institution level reference image catalogues of operational taxonomic units (OTUs) or morphospecies.

Monitoring mosaic biotopes in a marine conservation zone by autonomous underwater vehicle.

The number of marine protected areas (MPAs) has increased dramatically in the last decade and poses a major logistic challenge for conservation practitioners in terms of spatial extent and the multiplicity of habitats and biotopes that now require assessment. Photographic assessment by autonomous underwater vehicle (AUV) enables the consistent description of multiple habitats, in our case including mosaics of rock and sediment. As a case study, we used this method to survey the Greater Haig Fras marine conservation zone (Celtic Sea, northeast Atlantic).

Abyssal deposit-feeding rates consistent with the metabolic theory of ecology.

The Metabolic Theory of Ecology (MTE) posits that metabolic rate controls ecological processes, such as the rate of resource uptake, from the individual- to the ecosystem-scale. Metabolic rate has been found empirically to be an exponential function of whole organism body mass. We test a fundamental assumption of MTE, whether resource uptake scales to metabolism, by examining detritivores accessing a single common resource pool, an ideal study case.

MAIA-A machine learning assisted image annotation method for environmental monitoring and exploration.

Digital imaging has become one of the most important techniques in environmental monitoring and exploration. In the case of the marine environment, mobile platforms such as autonomous underwater vehicles (AUVs) are now equipped with high-resolution cameras to capture huge collections of images from the seabed. However, the timely evaluation of all these images presents a bottleneck problem as tens of thousands or more images can be collected during a single dive.

Episodic organic carbon fluxes from surface ocean to abyssal depths during long-term monitoring in NE Pacific.

Growing evidence suggests substantial quantities of particulate organic carbon (POC) produced in surface waters reach abyssal depths within days during episodic flux events. A 29-year record of in situ observations was used to examine episodic peaks in POC fluxes and sediment community oxygen consumption (SCOC) at Station M (NE Pacific, 4,000-m depth). From 1989 to 2017, 19% of POC flux at 3,400 m arrived during high-magnitude episodic events (≥mean + 2 σ), and 43% from 2011 to 2017.

Big in the benthos: Future change of seafloor community biomass in a global, body size-resolved model.

Deep-water benthic communities in the ocean are almost wholly dependent on near-surface pelagic ecosystems for their supply of energy and material resources. Primary production in sunlit surface waters is channelled through complex food webs that extensively recycle organic material, but lose a fraction as particulate organic carbon (POC) that sinks into the ocean interior. This exported production is further rarefied by microbial breakdown in the abyssal ocean, but a residual ultimately drives diverse assemblages of seafloor heterotrophs.

Landscape-scale spatial heterogeneity in phytodetrital cover and megafauna biomass in the abyss links to modest topographic variation.

Sinking particulate organic matter (POM, phytodetritus) is the principal limiting resource for deep-sea life. However, little is known about spatial variation in POM supply to the abyssal seafloor, which is frequently assumed to be homogenous. In reality, the abyss has a highly complex landscape with millions of hills and mountains.

Links between deep-sea respiration and community dynamics.

It has been challenging to establish the mechanisms that link ecosystem functioning to environmental and resource variation, as well as community structure, composition, and compensatory dynamics. A compelling hypothesis of compensatory dynamics, known as "zero-sum" dynamics, is framed in terms of energy resource and demand units, where there is an inverse link between the number of individuals in a community and the mean individual metabolic rate. However, body size energy distributions that are nonuniform suggest a niche advantage at a particular size class, which suggests a limit to which metabolism can explain community structuring.

Global reductions in seafloor biomass in response to climate change.

Seafloor organisms are vital for healthy marine ecosystems, contributing to elemental cycling, benthic remineralization, and ultimately sequestration of carbon. Deep-sea life is primarily reliant on the export flux of particulate organic carbon from the surface ocean for food, but most ocean biogeochemistry models predict global decreases in export flux resulting from 21st century anthropogenically induced warming. Here we show that decadal-to-century scale changes in carbon export associated with climate change lead to an estimated 5.

Feeding preferences of abyssal macrofauna inferred from in situ pulse chase experiments.

Climatic fluctuations may significantly alter the taxonomic and biochemical composition of phytoplankton blooms and subsequently phytodetritus, the food source for the majority of deep-sea communities. To examine the response of abyssal benthic communities to different food resources we simulated a food sedimentation event containing diatoms and coccolithophorids at Station M in the NE Pacific. In one set of experiments we measured incorporation of diatomC and coccoN into the macrofauna using isotopically enriched (13)C-diatoms and (15)N-coccolithophores.

Deep ocean communities impacted by changing climate over 24 y in the abyssal northeast Pacific Ocean.

The deep ocean, covering a vast expanse of the globe, relies almost exclusively on a food supply originating from primary production in surface waters. With well-documented warming of oceanic surface waters and conflicting reports of increasing and decreasing primary production trends, questions persist about how such changes impact deep ocean communities. A 24-y time-series study of sinking particulate organic carbon (food) supply and its utilization by the benthic community was conducted in the abyssal northeast Pacific (~4,000-m depth).

Biotic and human vulnerability to projected changes in ocean biogeochemistry over the 21st century.

Ongoing greenhouse gas emissions can modify climate processes and induce shifts in ocean temperature, pH, oxygen concentration, and productivity, which in turn could alter biological and social systems. Here, we provide a synoptic global assessment of the simultaneous changes in future ocean biogeochemical variables over marine biota and their broader implications for people. We analyzed modern Earth System Models forced by greenhouse gas concentration pathways until 2100 and showed that the entire world's ocean surface will be simultaneously impacted by varying intensities of ocean warming, acidification, oxygen depletion, or shortfalls in productivity.

The role of carrion supply in the abundance of deep-water fish off California.

Few time series of deep-sea systems exist from which the factors affecting abyssal fish populations can be evaluated. Previous analysis showed an increase in grenadier abundance, in the eastern North Pacific, which lagged epibenthic megafaunal abundance, mostly echinoderms, by 9-20 months. Subsequent diet studies suggested that carrion is the grenadier's most important food.

Deep-sea echinoderm oxygen consumption rates and an interclass comparison of metabolic rates in Asteroidea, Crinoidea, Echinoidea, Holothuroidea and Ophiuroidea.

Echinoderms are important components of deep-sea communities because of their abundance and the fact that their activities contribute to carbon cycling. Estimating the echinoderm contribution to food webs and carbon cycling is important to our understanding of the functioning of the deep-sea environment and how this may alter in the future as climatic changes take place. Metabolic rate data from deep-sea echinoderm species are, however, scarce.

Long-term reductions in anthropogenic nutrients link to improvements in Chesapeake Bay habitat.

Great effort continues to focus on ecosystem restoration and reduction of nutrient inputs thought to be responsible, in part, for declines in estuary habitats worldwide. The ability of environmental policy to address restoration is limited, in part, by uncertainty in the relationships between costly restoration and benefits. Here, we present results from an 18-y field investigation (1990-2007) of submerged aquatic vegetation (SAV) community dynamics and water quality in the Potomac River, a major tributary of the Chesapeake Bay.

Connections between climate, food limitation, and carbon cycling in abyssal sediment communities.

Diverse faunal groups inhabit deep-sea sediments over much of Earth's surface, but our understanding of how interannual-scale climate variation alters sediment community components and biogeochemical processes remains limited. The vast majority of deep-sea communities depend on a particulate organic carbon food supply that sinks from photosynthetically active surface waters. Variations in food supply depend, in part, on surface climate conditions.

Community change in the variable resource habitat of the abyssal northeast Pacific.

Research capable of differentiating resource-related community-level change from random ecological drift in natural systems has been limited. Evidence for nonrandom, resource-driven change is presented here for an epibenthic megafauna community in the abyssal northeast Pacific Ocean from 1989 to 2004. The sinking particulate organic carbon food supply is linked not only to species-specific abundances, but also to species composition and equitability.

Free-drifting icebergs: hot spots of chemical and biological enrichment in the Weddell Sea.

The proliferation of icebergs from Antarctica over the past decade has raised questions about their potential impact on the surrounding pelagic ecosystem. Two free-drifting icebergs, 0.1 and 30.

Abundance and size distribution dynamics of abyssal epibenthic megafauna in the northeast Pacific.

The importance of interannual variation in deep-sea abundances is now becoming recognized. There is, however, relatively little known about what processes dominate the observed fluctuations. The abundance and size distribution of the megabenthos have been examined here using a towed camera system at a deep-sea station in the northeast Pacific (Station M) from 1989 to 2004.

Shifts in deep-sea community structure linked to climate and food supply.

A major change in the community structure of the dominant epibenthic megafauna was observed at 4100 meters depth in the northeast Pacific and was synchronous to a major El Niño/La Niña event that occurred between 1997 and 1999. Photographic abundance estimates of epibenthic megafauna from 1989 to 2002 show that two taxa decreased in abundance after 1998 by 2 to 3 orders of magnitude, whereas several other species increased in abundance by 1 to 2 orders of magnitude. These faunal changes are correlated to climate fluctuations dominated by El Niño/La Niña.