OCEAN 6214/17/09 DISTRIBUTION PATTERNS OF BENTHOS

A.. Pollution gradients

B. Depth gradients

C. Biomass/primary-production gradients

Readings: Chapters 8 and 14 in Kaiser et al. (2005) Marine Ecology, Oxford U. Press.

Smith, C. R. et al. 2008. Abyssal Food Limitation, Ecosystem Structure and Climate Change. Trends in Ecology and Evolution 23: 518-528.

------------------------------------------------------------A. DEFINITIONS AND TERMINOLOGY

1) General Terminology

Benthos -- organisms living on or in the seafloor.

Benthopelagic -- (demersal), occurring in the water column near the seafloor, i.e., within the benthic boundary layer.

Epibenthic -- (epifaunal, epifloral), living at the sediment-water interface.

Infaunal -- living within the seafloor.

Interstitial -- occurring in pore spaces among sediment grains.

Psammon -- interstitial organisms.

2) Size Classes -- Soft Bottoms

Commonly used size limits for free-living, soft-bottom benthos include:

Nanobenthos = microbiota -- < 62 µm (shallow water)< 42 µm (deep sea)

Meiofauna -- 62 µm - 500 µm (shallow water)42 µm - 300 µm (deep sea)

Macrofauna -- 500 µm - 3 cm (shallow water)300 µm - 3 cm (deep sea)

Megafauna -- > 3 cm, or "large enough to be identifiedin bottom photographs."

All size classes are essentially defined operationally. The nanobenthic through macrofaunal size classes are determined by passage and retention on variously sized meshes (or screens). Thus, size limits are functions of the two smallest perpendicular body dimensions (i.e., length/width or aspect ratio) and body flexibility. NB. Screening efficiencies change markedly with preservation (often as much as 50% more live individuals pass through a given mesh) so do not vary preservation routine in the middle of a study. The time required to sort animals from a sediment sample is directly related to screen size, so non-standard sizes often are used to optimize sorting efficiency.

The lower limit for megafauna (and the upper limit for macrofauna) is determined by retention in trawl meshes, or identifiability in in situ photographs (at no standard distance).

Additional size related terms include:

Macrophyte -- plant visible to the unaided eye.

Microphyte -- microscopic plant.

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Pearson and Rosenberg, 1978

CT scan of subtidal Narragansett Bay sediment with large cerianthid anemone tube (Ceriatheopsis americanus), several small clams, and numerous polychaete tubes

Nearby polluted Narragansett Bay sediment with lone quahog (Mercenaria mercenaria)

Pearson and Rosenberg, 1978

Succession following a pulse of dredge-spoil dumping

SULFIDE AND Corg IN TOP 2 CM

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DISTANCE FROM WHALE (m)

Sulfide

% Organic Carbon

MACROFAUNAL ABUNDANCE

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DISTANCE FROM WHALE (m)

MACROFAUNAL DIVERSITY

00.10.20.30.40.50.60.70.80.9

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DISTANCE FROM WHALE (m)

IND

EX V

ALU

E

Shannon H'

Shannon J'

Rarefaction E(51)/20

Santa Cruz Basin whale fall (1674 m) Smith et al., 2002

t = 4.5 yr

Carney et al., 1983

Gage and Tyler, 1992

Rowe, 1983

Jumars and Gallagher, 1982

Rex et al., 2006. Global bathymetric pattern of standing stock and body size in the deep-sea benthos. Mar Ecol Progr Ser 317: 1-8.

Standing stock corrected for latitude and longitude (n=2310 from a total of 128 studies)

Psychropotes longicauda60 cm long holothurian

(5000 m central Pacific)

- Scavenging amphipods

- Scavenging fish (Priede et al., unpublished data)

- Deposit feeding holothurians?

(5000 m central Pacific)

Bigger - Deeper

Carney et al., 1983

Levinton, 2001

Gage and Tyler, 1991

Deep-sea suspension feeders are generally rare, tall, mostly passive, most abundant in areas of flow intensification

1 m

Smith et al., 1997

(Hessler et al., 1978)

9604 m, Philippine Trench

~ 24 kg bait removed in ~16 hours!

Example of “Bigger–Deeper” phenomenon --- scavenging amphipods (also occurs in rattail fish, isopods, and foraminiferans)

Eurythenes gryllus

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