Vertical Ecology of the Pelagic Ocean: Quantified Patterns and New Perspectives

Applications of acoustic and optical sensing and intensive, discrete-depth sampling, in concert with collaborative international research programs, have substantially advanced our knowledge of pelagic ecosystems in the 17 years since the last Deep-water Fishes FSBI Symposium. Although the epipelagic habitat is the best-known, and remote sensing and high-resolution modeling allow near-synoptic investigation of upper layer biophysical dynamics, ecological studies within the mesopelagic and deep-demersal habitats have begun to link lower and upper trophic level processes. Bathypelagic taxonomic inventories are far from complete but recent projects (MAR-ECO and CMarZ, supported by the Census of Marine Life program) have quantitatively strengthened distribution patterns previously described for fishes and provide new perspectives. Synthesis of net and acoustics studies suggests that the biomass of low-latitude mesopelagic fishes may be 2-3 orders of magnitude greater than the total global commercial fisheries landings. Inclusion of high-latitude mesopelagic and global bathypelagic fish biomass estimates suggests that the majority of Earth’s fish biomass may be deep-pelagic. Acoustics studies have detected pronounced deep-scattering layers well below 1000 m, while discrete-depth net sampling has documented deep-pelagic fish biomass maxima below 1500 m in some regions. Investigations of bathypelagic ecosystems demonstrate that gelatinous zooplankton, as well as other “alternate pathways,” are key trophic resources for deep-water fish production. Lastly, perhaps the most exciting discovery is that vertical interconnectivity among fishes throughout the water column is widespread. As Peter Herring (2002) remarked, “Every time we think we understand the [deep ocean] ecosystem and the organisms they manage to produce a new rabbit out of the oceanic hat, so that we are required to readjust our previous perspective.

Microzooplankton Grazing and Productivity in the Central and Southern Sector of the Indian River Lagoon, Florida

Microzooplankton grazing was measured with the dilution method in the central and southern sectors of the Indian River Lagoon during summer 2006 and 2007. Microzooplankton actively grazed phytoplankton during all experiments. Grazing rates averaged (± SD) 0.956 ± 0.19 d-1 and ranged from 0.54 to 1.36 d-1. Phytoplankton carbon, measured by microscopy, averaged 314 ± 251 μg C L-1 and ranged from 115 to 936 μg C L-1. Microzooplankton ingestion rates averaged 303 ± 260 μg C L-1d-1 and ranged from 90 to 907 μg C L-1d-1. Microzooplankton potential productivity, a first-order estimate of microzooplankton productivity, averaged 91 ± 78 μg C L-1d-1 and ranged from 27 to 272 μg C L-1d-1. Microzooplankton grazing rates were not related to salinity. In contrast, the magnitudes of phytoplankton carbon concentration, microzooplankton ingestion rate, and microzooplankton potential productivity were statistically significantly greater in lower (\u3c20 \u3epsu) salinity waters. An examination of data from another Florida estuary and other Gulf of Mexico coast estuaries suggests that microzooplankton productivity may, in general, be highest in lower salinity waters

Pelagic Habitat Use by Juvenile Reef Fishes in the Gulf of Mexico

The assemblage composition, abundance, frequency of occurrence, and vertical distribution of juvenile reef fishes in the offshore pelagic habitat of the northern Gulf of Mexico are described. This study, a component of the NOAA-supported Offshore Nekton Sampling and Analysis Program, is the first to examine juvenile reef fish distributions across the oceanic northern Gulf of Mexico after the Deepwater Horizon oil spill. Results presented here are derived from a 3-month, spring/summer research cruise in 2011 on the M/V Meg Skansi. A 10-m2 MOCNESS midwater trawl was used to sample 45 stations from the surface to a depth of 1500 m, both day and night. Seven reef fish orders, 30 reef fish families and 119 reef fish species were collected. Initial analysis has revealed the presence of juveniles of some species in locations where adults are not known to occur. Juveniles were found almost exclusively in the uppermost 200m of the water column. A greater number of individuals were collected in nighttime trawls. Surprisingly, some individuals were sampled between 1000–1500 m. During the MS7 sampling program, hydrographic profiles of the water column were recorded. This information provides the hydrographic background setting against which the coastal reef fish distributions in the offshore pelagic habitat of the Gulf of Mexico can be characterized. Results of fish distributions as a function of location (relative to the shelf break) and major mesoscale oceanographic features will be presented

Dispersion Overrides Environmental Variability as a Primary Driver of the Horizontal Assemblage Structure of the Mesopelagic Fish Family Myctophidae in the Northern Gulf of Mexico

The lanternfishes (Myctophidae) are a highly speciose, globally-distributed family of fishes that constitute a dominant component of the global pelagic fauna. As a vertically-migrating taxon of oceanic micronekton, myctophids play vital ecological roles in the biological carbon pump and as an important prey group for several commercially-important species. However, our knowledge of the ecology of this taxon remains incomplete, and as anthropogenic impacts continue to develop and extend into deeper waters, there is a clear need for a better understanding of its ecological role and assemblage dynamics. The aim of the present study was to examine the distribution patterns of the myctophid assemblage within a 200 km × 700 km grid of the northern Gulf of Mexico (GoM) in relation to major mesoscale hydrographic features. The 22 dominant myctophid species (\u3e0.05% by relative abundance) were analyzed from a total of 302 trawl samples collected between January and September 2011, from 0 to 1000 m depth. Redundancy analysis (RDA) indicated that measured environmental variables and spatial patterning explained an average of 12% (range: 0–27%) of the observed variance in the myctophid assemblage. Distance-based Moran’s Eigenvector Mapping (dbMEM) and trend analysis (RDA) indicated limited significant spatial coherence within the assemblage at the scales considered. Local contribution to beta diversity scores corroborated these findings, indicating that the majority of samples were not significantly different from the mean assemblage structure. Taken together, these results suggest that the myctophid assemblage in the northern GoM is well-mixed and highly dispersed at the sub-basin scale (at least), likely the result of the interaction between vertical migration and depth-specific lateral advection. Findings such as these inform our approach to assessing impacts in a large, dynamic, pelagic ecosystems. It is essential to know over what spatial scales assessments of pelagic faunal impacts, and potential recoveries, must be based. In cases of large, spatially integrated pelagic assemblages, high dispersal rates may serve to either ameliorate the effects of a disturbance through immigration or spread the effects across a wider spatial area than the disturbance phenomenon footprint itself

Who\u27s Eating Whom? Identification and Quantification of Deep-Pelagic Prey Fishes in the North Atlantic Ocean

Understanding the structure and functioning of marine ecosystems requires accurate knowledge of trophic interactions. Trophic ecology studies generally underestimate prey diversity due to the difficulties imposed by digestion. Further, this degradation leads to uncertainty in the quantification of prey biomass (i.e., energy flow between various ecosystem components). Trophic interactions in the deep sea are poorly known relative to coastal ecosystems due to an incomplete inventory of meso-and bathypelagic species composition. The CoML field project MAR-ECO has increased our knowledge of the faunal structure of the mid-North Atlantic. Deep-pelagic fish specimens from the 2004 MARECO expedition provided a basis for an anatomical reference collection, described here, which will allow a better understanding of interactions among higher trophic levels. A library of 1674 images of diagnostic ‘hard part’ anatomical features (e.g. dentaries, otoliths, premaxillae) from 40 species of meso-and bathypelagic fishes has been compiled, with corresponding length and weight regressions for each feature. The aims of this project are to increase the taxonomic resolution of trophic analyses and gain insight into ecosystem functioning as it relates to biodiversity in deep-marine habitats

New Species of Eustomias (Teleostei: Stomiidae) from the Western North Atlantic, with a Review of the Subgenus Neostomias

A new species of the deep-sea dragonfish genus Eustomias is described from 14 specimens from the western North Atlantic. This species belongs to the subgenus Neostomias, which is defined principally by the presence of a single pectoral ray, plus one small rudimentary ray. It is unique among members of the subgenus in having a combination of characters that includes a short mental barbel, multiple proximal bulbs on the barbel main stem, and a unique terminal bulb morphology. Analysis of similar species warrants resurrection of Eustomias monodactylus, previously placed in synonymy with Eustomias filifer. A revised key to the species of the subgenus Neostomias is provided

Species Composition, Abundance, and Vertical Distribution of the Stomiid (Pisces: Stomiiformes) Fish Assemblage of the Gulf of Mexico

Species composition, abundance, and vertical distribution of the stomiid fish assemblage were investigated in the eastern Gulf of Mexico, a low-latitude, oligotrophic oceanic ecosystem. Seventy-two described species, representing 18 genera, and one undescribed species were identified from 1155 trawl samples. With an additional 10 species reported elsewhere, the stomiid species number now known equals 83, making the Stomiidae the most diverse fish family in the Gulf of Mexico. The assemblage was dominated by three species,Photostomias guernei, Chauliodus sloani and Stomias affinis. These species, as well as four other common species, exhibited an asynchronous diel vertical migration pattern (450–900 m during day; 20–300, 550–900 m at night). The percentage of the populations of the three dominant species migrating daily ranged from 50–70%. Two other patterns occurred in less abundant species: synchronous migration (400–700 m during the day, 0–200 m at night); and, possible migration from the bathypelagial (\u3e 1000 m during day; 50–300 m at night). Minimum abundance and biomass estimates for the entire assemblage were 1.86 × 105 individuals and 35.3 kg DW•km-2 in the upper 1000 m. Stomiids comprised approximately 10% of the micronekton standing stock in the eastern Gulf. Extrapolating eastern Gulf data to the world warm-water mesopelagial, abundance results suggest that stomiids are the dominant mesopelagic upper-trophic level predatory fishes, and as such may serve as key trophic mediators in the transfer of energy in these ecosystems

Who Is Eating Most of the Zooplankton in the Oceanic Gulf of Mexico? The Impact of Mesopelagic Fishes

Deep-sea pelagic fishes are the most abundant vertebrates on Earth, yet their role in the overall economy of these is poorly known. Low latitude oligotrophic regimes, typified by the eastern Gulf of Mexico, constitute most of the world ocean and consequently support the largest global ecosystems. Thus, we have little information on the trophic role of most of Earth\u27s vertebrates. To address this, the diets of an entire midwater fish assemblage (164 species, constituting \u3e 99% of assemblage numbers) were analyzed to assess feeding guilds and predation impact. Zooplanktivory was the dominant feeding mode (80% of prey biomass taken), followed by piscivory. However, the entire fish assemblage predation impact on zooplankton was only 5-10% of daily production. This points to critical limitations in our understanding of how tropical - subtropical regimes, the largest of global ecosystems, function and which taxonomic groups are the most important zooplanktivores. Regarding the latter, the obvious candidate is other zooplankton, including large gelatinous predators