GEOL 2503 Introduction to Oceanography
Dr. David M. Bush
Department of Geosciences
University of West Georgia
POWERPOINT SLIDE SHOW NOTES
Topic 24. Benthos
1 Topic 24. Benthos
2 Characteristics of the benthos
3 Other Characteristics
4 Benthos dominated by three Kingdoms
5 Life styles of the benthos
6 Benthic environments
7 The Hedgpeth classification for review
8 Benthos can be divided into two ecosystem types
9
The following slides are examples from the photosynthetic ecosystem: sessile marine algae at low tide
10
Algae have similarity in form to plants, but are quite different. Algae lack a vascular system. That is, algae have no internal system to transport water, dissolved minerals, and food. Algae exchange nutrients and waste through their cell walls. Holdfasts look like roots but they do not take up water and minerals as do roots in plants. Holdfasts are simply attachment mechanisms. Stipes look like stems and blades look like leaves, but they are much simpler. Thallus refers to the entire mass of tissue. Alga is singular form of algae.
11 Kelp beds provide food and shelter (similar to forests and shrubs on land).
12
13
Recall that sargassum weed has floats, but it is planktonic. Kelp is sessile, and the floats keep the plant erect in the water column to aid in gathering sunlight.
Thalassia is a true plant with roots and a vascular system. The common name is turtle grass.
14 Salt marsh thrives in intertidal areas.
15 Mangroves fill the same niche as salt marsh, but in tropical environments.
16 Mangroves
17 Mangroves
Sessile organisms are attached. Solitary means they live on their own. Some organisms
18 are colonial where cells organize to perform a certain function, but they are not organs.
Mussels may live gathered together in large groups, but the animals are each separate individuals.
19
20
Featherduster worms can pull their bodies back inside worm tubes when disturbed. The crowns extending from the tubes are tentacles to gather food and contain gill structures.
The individual coral animals are called polyps. Each pore on a coral skeleton contains a coral polyp.
21 Sponges are primitive colonial animals
22 Water is drawn into barrel sponge and flushes out through the central cavity.
23 Oysters are solitary even though they can grow together into a massive oyster bank.
24 Barnacles are solitary and sessile.
25 Giant clam
26 Protista are not common members of the benthos.

27
32
Coral reefs are complex colonies. It is at the same time an animal, a vegetable, and a mineral. The animal is the coral polyp. There are single-celled plants living in the coral tissue. And the skeletal framework of the coral is calcite. Corals thrive in warm clear water.
28
There are many types of corals in different shapes and sizes. Reefs are commonly zoned with more massive forms on the windward side.
29 Coral reefs are restricted to tropical and subtropical environments.
30 The beauty of reefs is largely hidden below sea level.
31 Reefs are highly productive, complex ecosystems.
Corals are related to jellyfish and sea anemones. They all have stinging cells to trap prey.
Living in the tissue are zoothanthellae, photosynthetic dinoflagellates which pass carbon dioxide to the corals. Carbon dioxide is needed to secrete the calcite coral skeleton. The skeleton is make of calcite, CaCO 3 .
33 Coral polyp anatomy.
34 Elkhorn coral
35 Staghorn coral
36 Brain coral
Sea whips are also corals but do not secrete a skeleton. They are called soft corals.
37 Corals which secrete skeletons are called stony corals. The bright orange blob is an encrusting sponge.
38 Remember Charles Darwin and atolls.
39
The lagoon at the center of an atoll may have small circular patch reefs in addition to the reefs surrounding the lagoon. Also, windward and leeward sides are common.
40 An atoll from the air.
41 Some vagrant benthos can swim for short distances.
42 Most vagrant benthos crawl along the bottom.
43 Scallops can jet water to move around the sea bottom.
44 Red shrimp
45
The ghost shrimp is very common on the Georgia shore. Look for its characteristic burrows at low tide.
46
Christmas Tree worms are similar to the featherduster worms except these bore into coral or other hard substrate.
47 Clams a good burrowers into sandy sediment.
48 Ghost crab
49 There are many types of starfish.
50 Diadema has barbed spines containing an irritant. Not good if you step on one.
51 Worms are present at all ocean depths.
52 Different animals live at different water depths.
53 Now the chemosynthetic ecosystem.
54
55
Recall hydrothermal vents from plate tectonics. Just as photosynthetic organisms derive energy from sun light, chemosynthetic organisms derive energy from minerals dissolved in sea water.
Tube worms are one of the odd animals found during investigations of the mid-ocean ridge and associated hydrothermal vents. They can grow to over two meters high, and have no mouths or digestive system. They absorb nutrients through their skin.
Hemoglobin gives their tissue the dark red color.
56 Tube worms
57 Clams

58 Clams
59 Intertidal faunal zonation
60 Marine algae anatomy
61 Faunal zonation in the nearshore.
62 Reef zonation