Dear Sven

Distribution of benthos along oceanic depth gradient is influenced by a number of factors including the ambient water temperature, dissolved oxygen concentration, sediment type (grain size), total organic carbon present in the sediment, etc. However, the most influential factor is the availability of food, may be in terms of productivity of the overlying water or the deep-sea current pattern (that brings in food particles) etc. Accordingly there will be an associated difference in the trophic structure in the deep-sea communities. In general, there is a drop in species diversity along the oceanic depth gradient.

Following are some literature of your interest:

1. http://nopr.niscair.res.in/bitstream/123456789/14174/1/IJMS%2041(3)%20272-278.pdf

2. http://www.biologiatropical.ucr.ac.cr/attachments/volumes/vol44-2A/35_Jimenez_Benthic_macrofauna.pdf

3. http://drs.nio.org/drs/bitstream/2264/562/1/Environ_Monit_Assess_125_459.pdf

4. http://nopr.niscair.res.in/bitstream/123456789/4670/1/IJMS%2038(2)%20191-204.pdf

5. http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0014491

Best

Dola

One important variable that changes with Ocean depth is light availability. The deeper the ocean strata the lesser the dependence of benthic organisms on light and the more divergent the food options will be.

For the larger organisms adaptations to pressure and navigation at the ocean depths will also determine the occurrence of organisms.

Dear kerwath

The benthic fauna can change their distribution based on the following important factors

1. Sediment Pattern

2. TOC

3. Dissolved oxygen

4. Pressure

5. Depth

6. Temperature

and etc.

All the parameters are interlinking with benthic faunal distribution.

Feeding type of macrofauna is depending on the sediment distribution.

Food availability is depending upon TOC and water current through the settling of organic carbon material in the bottom. Dissolved oxygen is also one of the factor to control the abundance and diversity of benthic organisms. in some places (Eastern pacific, north Indian Ocean and east Atlantic) Oxygen minimum zone is occurring (

What depth ranges are you interested in?

Ten to 500 m, down the slope of a shallow seamount.

Sven,

I'm much more familiar with deeper soft bottom systems which have a somewhat engimatic mid-slope diversity maximum. There is quite a lot of seamount activity now. A good starting point in the literature is

http://www.plosone.org/article/info:doi/10.1371/journal.pone.0032031

Within your depth range the most likely factors in my opinion will be light, water velocity, and temperature. This assumes that you are dealing with hard substrate over the entire range. Your system will definitely experience a photic-dysphotic gradient. Water velocity impinging on bottom will also decrease with depth. At the upper end of the depth range, most water movement may be in the form of orbital velocity under the surface wave field rather than advective currents. Depending on where your system is, 500m should be as cool as 6C or colder in contrast to a seasonally warmer 10m depth.

My limited familiarity with seamount work leads me to believe that those systems have much more in common with continental margins than previously appreciated. That being the possible case, you might explore literature on mesophotic reefs and hardbottoms.

Good luck with your work.

Bob Carney

Thank you for all your useful comments. I will provide data in this forum after our expedition.

There are a lot of factors that can affect benthic biodiversity along a depth gradient like water temperature, light availability, oxygen (and other elements) concentration and pressure. If you want to observe benthic biodiversity at varying ocean depths, I would suggest that you monitor the distribution and activity patterns of bacteria that are inhabiting the area. Through microbiological and biochemical methods, you can follow the community shifts of bacteria at different ocean depths. This would reveal a lot about the state and condition of that part of the benthos.

This is an interesting paper I found that might be relevant to your study:

http://www.mbari.org/news/publications/ar/chapters/08_BenthicBiodiversity.pdf

And also this study about a long-term observation of benthic activities in central Japan might aid in your own expedition:

http://www.oceanobs09.net/proceedings/ac/FCXNL-09a02-1646360-1-KITAZATO%20et%20al%20Ocean%20Obs_withFigs2.pdf

Hello! I have also learned so much from the answers given by the other doctors and scientists and I would also like to share some information that I aware of...

The ocean, due to its vastness and different environmental conditions and factors, results to different niches that house a high benthic biodiversity. Both physical (i.e. light and temperature) and chemical conditions (i.e. salinity and oxygen), with their respective different gradients throughout the ocean, causes different types of mini biomes and ecosystems that have diverse levels of nutrient availability and conditions suitable to distinct organism types. The effects of light, temperature, salinity, and oxygen in the aquatic environment are four of the main determinants of the environmental conditions in each oceanic gradient.

1. Light- most of the light (approximately 80%) reach only up to the upper surface of the epipelagic zone. Thus, most euphotic organisms thrive here.

2. Temperature- warm water (upper part of the ocean) and cold water (lower part) results to a phenomenon called thermal stratification. However, events such as upwelling causes the mixing of the two layers (cold water goes up and warm water goes down), and the movement of nutrients across the gradients.

3. Salinity- there are diverse ranges of salinity across different latitudes. For example, salinity is highest along the subtropical regions as there is a higher rate of evaporation there than that of precipitation

4. Oxygen- it has been studied that the upper and lower oceanic gradients have the highest amount of oxygen.

These all affects the benthic biodiversity as different distributions of essential nutrients and resources are present in diverse oceanic depths. And aside from these four factors, a lot more should be taken into account in order to fully determine the changes of biodiversity. I really hope this helps!