Extreme ecosystem studies in the deep ocean
Technological developments

 
      

 
 
WP2 - Quantitative imaging


EXOCET/D project is putting a large emphasis on imagery (WP2) because this tool is of central importance for deep-sea biological studies.

WP 2.1 Assessing spatial variability at small scales

Ecology has to consider scale issues because organisms and habitats are rarely homogeneous and heterogeneity makes ecological variables and processes scale-dependent. This is particularly true in deep sea chemosynthetic habitats (hydrothermal vents, whale bones, seeps) that exhibit high spatial variability of both species distribution and abiotic factors at relatively small-spatial scales.

Imaging tools permit the non-destructive, cost effective acquisition of ecological information at different spatial scales in the marine environment. The main objective of WP2.1 is to set-up a complete methodology to make reconstructions of small-scale scenes from underwater video imagery. Overall, the development of stereovideography techniques will permit the reconstruction of 3D maps of species distribution and environmental variability, at scales ranging from 0.5 to 2 meters and to link visual biological data to chemical and physical measurements.

East Pacific Rise, the red dots are laser spots spaced of 20 cm to scale the picture, PHARE cruise . ŠIfremer.


WP2.2 Time-series studies in marine ecosystems

There is world-wide recognition for the need of long term in situ monitoring of the marine environment. While the intertidal zone and coral reefs have retained much attention because of their accessibility, technological limitations have delayed observational studies in the deep ocean. Only recently are we beginning to understand some of the dynamics of deep-sea communities. Even more important, most of the traditional techniques used to evaluate the influence of biological interactions are not yet applicable in deep-sea habitats. As a result, our knowledge of the influence of different factors in these ecosystems is extremely limited compared to shallower environments.

Particularly lacking in the study of abyssal benthic communities are time-series data. Time-series studies provide a means of studying organism growth, faunal succession, biological interactions and the response of species and communities to natural environmental changes. Understanding community dynamics is also an important prerequisite for management, conservation and protection of natural ecosystems. The development of new autonomous scientific tools, suited for long-term deployment, is an essential step to insure the success of these future observatories.

Temperature time series obtained during 8 months on a community of hydrothermal mussels in the Mid Atlantic Ridge. ŠIfremer

 

A major goal of WP 2.2 is to design a long-term imaging module equipped with a deep-sea autonomous video camera, adequate lightning and sufficient energy storage. In parallel to the development of the video module, the technology will be used to develop a macrophotography module, equipped with in situ setting controls and designed to be manipulated with a ROV.
 


WP2.3 Integration of acoustic and optic imagery at intermediate spatial scales


Backscatter signals from single and multi-beam sonars can be used for automated, swath mapping of habitat over large areas of seafloor, at scales that go well beyond what can be practicably achieved with optical imagery. Acoustic imaging techniques are finding new applications in benthic habitat mapping. However, in spite of tremendous progress done in the field, much work remains to fully explore the complementarity of optic and vision imagery to classify seabed communities and assess their spatial extent, and to generate accurate digital terrain maps.


The goal of this WP is to evaluate the potential of using sonar data to study deep-sea community changes and to explore their complementarity with video imagery. This work will build on previous research efforts on the analysis and classification of subbottom sediment layers using bottom-penetrating sonar.
 

In addition, there is currently great interest in the development of techniques and instrumentation to automate marine habitat mapping processes. The problem of overlaying the different data sets (for example, sidescan, profiler and vision data) to generate composites of benthic ecosystem and bottom types can be resolved by resorting to advanced sensor fusion techniques. Resulting information can be made available to scientists using Geographic Information Systems (GIS). This WP aims at developing and demonstrating selected techniques for accurate digital terrain mapping.