Mission Plan
Mission Plan

Education
Education

Overview
Overview

Technology
Technology

Serpentinization
Serpentinization

Chimney Formation
Chimney Formation

Sampling Technology
Sampling Technology

Microbial Habitat
Microbial Habitat

Fluid Chemistry
Fluid Chemistry

Macrofauna
Macrofauna

Explorers
Explorers

Desmophyllum

Desmophyllum. Fauna inhabiting Lost City Click image for larger view and image credit.


Lost City Macrofauna

Timothy Shank
Assistant Scientist
Biology Department
Woods Hole Oceanographic Institution

Kate Buckman
Graduate Student
WHOI/MIT Joint Program in Oceanography

When the Lost City Hydrothermal Field first emerged in the lights of a submersible in 2001 the venting spires did not appear to teem with life like most other vent fields around the world. There were no large red tubeworms, fields of clams or mussels typical of eastern Pacific vents or massive swarms of shrimp common to vents along the Mid-Atlantic Ridge. Yet in 2003, recovered pieces of Lost City chimney spires revealed numerous animals less than an eighth of an inch long. To date, over 70 potential species have been identified from Lost City, a surprisingly high biodiversity which is more than double the number of species found on vent chimneys typical of the Mid-Atlantic Ridge.

Synaphobranchus kaupi

Synaphobranchus kaupi. Fauna inhabiting Lost City. Click image for larger view and image credit.


The Lost City vent site may look barren at first glance, but look a little deeper, into the cracks and crevices of the carbonate through a microscope and the animals become obvious. Tiny invertebrates dwell within the cracks of these highly sculpted and actively venting porous carbonate structures. Gastropod snails, shrimp-like crustaceans (including amphipods that migrate daily from the upper surface waters to the Lost City area), and numerous polychaete worms (of which there are at least five new species) all live here. Nematode worms, flea-like ostracods, and small bivalves can also be found on these amazing structures. The biomass (net weight of animals) is small compared to a typical hydrothermal vent on the Mid-Atlantic Ridge. The biggest contributors to the biomass at Lost City are the larger more mobile megafauna, including the (grouper-like) wreckfish; cut-throat eels; and large red geryonid crabs, all readily visible around the spires.

Hydrothermal vent sites around the world host animals that are endemic, animals that are found living only in these vent areas. A pattern exists where typical vent areas exclude almost all other general deep-sea animals for some distance from hydrothermal activity. Non-venting habitats less than a few meters away (e.g., the sides of inactive solidified carbonate structures, sedimented areas, and breccia cap rock just to the north of the field) are dominated by hard corals (Lophelia pertusa and Desmophyllum), octocorals (gorgonians), galatheid crabs, turrid gastropods, foraminifera, pteropods, urchins, asteroids, ophiuroids, and typical deep-sea barnacles. Vent and non-vent habitats are strongly segregated at the Lost City.

wreckfish

This wreckfish, swimming between carbonate chimneys, is just over 1 meter in length. They are common near the summit of the massif and within the Lost City Field at a depth of ~750-800 m. They routinely followed the submersible Alvin during many dives in 2003. Click image for larger view and image credit. (HR)


Crab at Lost City

This crab was recovered from the edge of the Lost City field in 2003 at a water depth of ~ 750 m. Animals of this size are rare within the field. Although total biomass is small the diversity of fauna is as high or higher than that of black smoker sites along the Mid-Atlantic Ridge. Click image for larger view and image credit. (HR)


The combination of vent and non-vent habitats found in this location and the unique chemistry driving the system make it especially interesting to biologists. At present, we have barely scratched the surface of the biological diversity Lost City has to offer us, as well as the ecology of the animals that are found there. This expedition will provide animal and chemical samples necessary to identify how these communities and their habitat may have changed in the past 2 years, to identify new species, to examine the trophic relationships, and to learn what the various animals are feeding on. We will also use the samples to identify and compare the potentially novel ecological and evolutionary (genetic) relationships among the species living in the relatively shallow and isolated Lost City hydrothermal field to those living at the seven other known vent fields in the Atlantic.