About the Cover
Cover
The deep sea is, in general, sparsely occupied; but in restricted areas and under unusual conditions, such as cold seeps, vents, and seamounts, dense communities do exist and persist for generations. Sparse populations also aggregate temporarily to facilitate mating, breeding, and brooding, and such reproductive aggregations are well known in various habitats-but not in the deep sea, where only three such aggregations have previously been documented.
In this issue of The Biological Bulletin (p. 1), Jeffrey C. Drazen and colleagues at the Monterey Bay Aquarium Research Institute (MBARI, California) describe, for the first time in the deep sea, a multispecies reproductive aggregation-or reproductive hot spot-with an unusually high population density and biomass. This aggregation is featured on the cover; it is located in 1500-1600 meters of water on the Gorda Escarpment, a submarine plateau off Cape Mendocino in northern California. The site was discovered in the course of 15 exploratory dives by MBARI's remotely operated vehicle (ROV) Tiburon (top left image on the cover); the vehicle's two main cameras are identifiable by the white protective collars around their glass domes. The map on the cover locates the hot spot (red circle), Cape Mendocino (red dot), and the ROV dives (the line of small, irregular black areas extending westward).
Reproductive aggregations of two species-an octopus (Graneledone sp.), and a fish, the blob sculpin (Psychrolutes phrictus)-co-occurred at this site. The bottom left image shows three octopuses (body width, ~16 cm) in a characteristic brooding position; their eggs are underneath them, attached to the rock outcrop. Also attached are several anemones of various species; the crab is Chionocetes sp. The image at the top right shows octopus eggs (length, 40 mm) being sampled by the suction sampler on the ROV. Many of the eggs hatched during sampling; one hatchling appears in the sampler tube, and another is swimming away.1 In the lower right image-watching from behind a rock, which is covered in brisingid sea stars and anemones-is a blob sculpin (length, ~60 cm) with a nest of large, pinkish eggs behind it. Another fish is just visible in the upper left corner of the image. Most blob sculpins were seen attending to their egg masses (e.g., Fig. 3A, p. 4), the first direct observations of parental care by an oviparous deep-sea fish.
The particular location of this reproductive hot spot could be due to environmental heterogeneity; that is, the animals were concentrated at the crest of the local topography and near cold seeps. In these situations, they might benefit from enhanced current flow and local productivity, critical resources for reproductive success in the deep sea, where oxygen tension is very low and food is in short supply. Thus, for some deep-sea species, the fortuitous occurrence of critical environmental features may be essential for reproduction.
The four images are frames selected from videos taken during dives in 2001 and 2002. The videos were produced collaboratively by the crew of the support ship R/V Western Flyer, the ROV Tiburon pilots, and the scientists. Photo credit is to MBARI. Jeffrey C. Drazen contributed to the cover and legend. The final cover was designed by Beth Liles (Marine Biological Laboratory, Woods Hole, Massachusetts).
1The octopus hatchlings are being described by Janet Voight (Chicago Field Museum), an MBARI collaborator.
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Copyright © 2003 by the Marine Biological Laboratory.
