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Corals and sponges in rocky deep-sea environments are foundation species postulated to enhance local diversity by increasing biogenic habitat heterogeneity and enriching local carbon cycling. These key groups are highly vulnerable to disturbances (e.g., trawling, mining, and pollution) and are threatened by expansive changes in ocean conditions linked to climate change (acidification, warming, and deoxygenation). Once damaged by trawling or other disturbances, recolonization and regrowth may require centuries or longer, highlighting the need for stewardship of these deep-sea coral and sponge communities (DSCSCs). To this end, the sustainability of DSCSCs may be enhanced not only by protecting existing communities, but also repopulating disturbed areas using active restoration methods. Here, we report one of the first studies to explore methods to restore deep-sea coral populations by translocating coral fragments of multiple coral species. Branches of deep-sea corals were collected by ROV from 800 to 1300 m depth off central California and propagated into multiple fragments once at the surface. These fragments were then attached to “coral pots” using two different methods and placed in the same habitat to assess their survivorship (n = 113 total fragments, n = 7 taxa, n = 7 deployment groups). Mean survivorship for all translocated coral fragments observed within the first 365 days was ∼52%, with the highest mortality occurring in the first 3 months. In addition to an initial temporal sensitivity, survival of coral fragments varied by attachment method and among species. All coral fragments attached to coral pots using zip ties died, while those attached by cement resulted in differential survivorship over time. The latter method resulted in 80–100% fragment survivorship after 1 year for Corallium sp., Lillipathes sp., and Swiftia kofoidi, 12–50% for the bamboo corals Keratoisis sp. and Isidella tentaculum, and 0–50% for the bubblegum corals Paragorgia arborea and Sibogagorgia cauliflora. These initial results indicate differences in sensitivities to transplanting methods among coral species, but also suggest that repopulation efforts may accelerate the recovery of disturbed DSCSCs.

Carrying assorted cargo and covered with paints of varying toxicity, lost intermodal containers may take centuries to degrade on the deep seafloor. In June 2004, scientists from Monterey Bay Aquarium Research Institute (MBARI) discovered a recently lost container during a Remotely Operated Vehicle (ROV) dive on a sediment-covered seabed at 1281 m depth in Monterey Bay National Marine Sanctuary (MBNMS). The site was revisited by ROV in March 2011. Analyses of sediment samples and high-definition video indicate that faunal assemblages on the container’s exterior and the seabed within 10 m of the container differed significantly from those up to 500 m. The container surface provides hard substratum for colonization by taxa typically found in rocky habitats. However, some key taxa that dominate rocky areas were absent or rare on the container, perhaps related to its potential toxicity or limited time for colonization and growth. Ecological effects appear to be restricted to the container surface and the benthos within ∼10 m.

A study was conducted on the impacts of the presence of the Acoustic Thermometry of Ocean Climate (ATOC)/Pioneer Seamount cable on the benthos from nearshore waters adjacent to its origin at Pillar Point Air Force Station in Half Moon Bay, California to its terminus 95 km along its length on Pioneer Seamount. The coaxial Type SD cable was installed, unburied on the seafloor in 1995. Thirteen sites along the cable route were surveyed using the Monterey Bay Aquarium Research Institute (MBARI) ROVs Ventana and Tiburon equipped with cable-tracking tools. Quantitative comparisons of biological communities and seafloor features between cable and control sites were performed at nine stations. Forty-two hours of video footage and 138 push cores were collected over 15.1 km of seafloor. Approximately 12.1 km of the cable was observed (13% of the cable route). This study documents the appearance and condition of the cable and the underlying seafloor, and the effects of the cable on biological communities along its route. Limited self-burial of the cable has occurred during the 8-year deployment, particularly over the continental shelf and upper slope. Cable strumming by nearshore wave action has incised rocky siltstone outcrops. Several observations of kinks and snags in the cable on the upper slope (∼240 m depth) suggest contact with trawling gear. Few changes in the abundance or distribution of benthic fauna were detectable from video observations (epifaunal) and sediment core samples (infauna). Of 17 megafaunal groups and 19 infaunal taxa, no tests evaluating the overall effect of the cable were statistically significant. While these results indicate that the biological impacts of the cable are minor at most, three megafaunal groups exhibited cable-related changes at one or more stations. Actiniarians (sea anemones) colonized the cable when it was exposed on the seafloor, and were therefore generally more abundant on the cable than in surrounding, sediment-dominated seafloor habitats. Some fishes were also more abundant near the cable, apparently due to the higher habitat complexity provided by the cable. The study also documents general changes in the benthos across the Central California continental margin.

The distribution of excess 210Pb in 31 sediment cores was used to determine modern (last 100 yr) mass accumulation rates and the depth of sediment mixing on the continental shelf between Pacifica and Monterey, California, USA. Apparent mass accumulation rates average 0.27 g cm−2 yr−1 and range from 0.42 g cm−2 yr−1 to 0.12 g cm−2 yr−1. Accumulation rates were highest at mid-shelf water depths (60–100 m) adjacent to major rivers and near the head of the Ascension submarine canyon. Cores from water depths of less than 65 m had low, uniform 210Pb activity profiles and sandy textures. The uppermost 5–13 cm of 15 cores had uniform 210Pb activity profiles above a region of steadily decreasing 210Pb activity. This phenomenon was attributed to sediment mixing. The thickness of this upper layer of uniform 210Pb activity decreased southward from 13 cm, west of Pacifica, to less than 5 cm, near Monterey Canyon. This southward decrease may be attributed to shallower bioturbation in the southern study area. Integrated excess 210Pb activities were generally higher where sedimentation rates were high. They were also higher with increasing distance from major rivers. Thus, sedimentation rate alone does not explain the distribution of integrated excess 210Pb in this study area. Excess 210Pb in the seafloor is controlled by other factors such as sediment texture, the atmospheric deposition rate of 210Pb, and the residence time of sediment particles in the water column.

Age determination and validation studies on deep-water marine fishes indicate they are difficult to age and often long-lived. Techniques for the determination of age in individual fish includes growth-zone analysis of vertebral centra, fin rays and spines, other skeletal structures, and otoliths (there are three sets of otoliths in most bony fish semicircular canals, each of which is made of calcium carbonate). Most have regular increments deposited as the fish (and its semicircular canals) grows. The most commonly used otolith for age determination is the largest one called the sagitta. Age validation techniques include: (1) tag-recapture, often combined with oxytetracycline injection and analysis in growth-zones of bone upon recapture; (2) analysis of growth-zones over time; and (3) radiometric approaches utilizing a known radioactive decay series as an independent chronometer in otoliths from bony fishes. We briefly summarize previous studies using these three validation approaches and present results from several of our radiometric studies on deep-water, bony fishes recently subjected to expanding fisheries. Radiometric age validation results are presented for four species of scorpaenid fishes (the bank, Sebastes rufus, and bocaccio, S. paucispinis, rockfishes, and two thornyhead species, Sebastolobus altivelis and S. alascanus). In addition, our analysis of scorpaenids indicates that longevity increases exponentially with maximum depth of occurrence. The reason that the deep-water forms of scorpaenid fishes are long-lived is uncertain. Their longevity, however, may be related to altered physiological processes relative to environmental parameters like low temperature, high pressures, low light levels, low oxygen, and poor food resources.

To improve the accuracy and precision of radiometric age determination using 210Pb:226Ra disequilibria in otoliths of fishes, a technique was developed incorporating an ion-exchange procedure followed by isotope-dilution thermal ionization mass spectrometry (TIMS) to determine 226Ra. This technique counts ionized radium atoms directly; therefore, the uncertainty of the technique is superior to conventional radio-decay dependent techniques. Calcium and barium are major components of the otolith matrix that can interfere with TIMS analysis of radium. To remove these interferants, an ion-exchange separation procedure was developed. This procedure was tested by applying it to otolith samples from three fish species in three separate radiometric ageing studies. The resultant separations and TIMS determinations indicate that the procedure efficiently separates radium from calcium and barium. Measured 226Ra activities for each species were similar to previous radiometric ageing studies, with the exception of one sample. When results were compared with traditional 226Ra determination techniques, radon emanation and α-spectrometry, the separation procedure with isotope-dilution TIMS had significant advantages. Samples over three times smaller than attempted in other studies were processed with decreased uncertainty and processing time.

The Davidson Seamount is located 120 km to the southwest of Monterey, along the California coast, USA. It is 2,400 m tall; yet, it is still 1,250 m below the sea surface. In May 2002, 90 hours of digital video was recorded from all depths of the Davidson Seamount, using a remotely operated vehicle, and deep-sea coral specimens were collected. Preliminary analyses indicate that 20 coral taxa were found, and they were almost exclusively located in high relief, ridge areas. Other species were noted on or adjacent to the corals. Because of its pristine nature, as well as human threats and great potential for education, the Davidson Seamount is under consideration for protection as part of the Monterey Bay National Marine Sanctuary.

Longevity estimates for the bocaccio rockfish (Sebastes paucispinis) using traditional techniques range from less than 20 years to approximately 50 years. Otoliths of bocaccio are difficult to age, and previous attempts to validate ages have been unsuccessful. Because otolith age suggests the bocaccio are reasonably long-lived, lead–radium dating was used in an attempt to independently age bocaccio otoliths. The measured 210Pb and 226Ra activities were among the lowest reported and resulted in poor radiometric age resolution; however, the break-and-burn technique clearly underestimated age in some cases with the longevity of the bocaccio being at least 31 years. To provide better age resolution, the bomb radiocarbon approach was applied to individual otoliths. Based on measured radiocarbon levels relative to a reference time-series, several specimens were aged at approximately 30–40 years. To evaluate these determinations, the remaining otolith of the pair was sectioned and aged blind. The result was an excellent fit to the reference time-series and a validation of the age estimates. The maximum age from growth zone counts was 37 ± 2 years, which is consistent with a reported maximum age of approximately 50 years.

With proper manipulation of pH, the hemoglobin of a deep water fish can inject oxygen up against several hundreds of atmospheres.