12 Seaweeds, Sea Grasses, and Benthic Microorganisms Notes for Marine Biology: Function,...
-
Upload
mitchel-cochran -
Category
Documents
-
view
216 -
download
2
Transcript of 12 Seaweeds, Sea Grasses, and Benthic Microorganisms Notes for Marine Biology: Function,...
12 Seaweeds, Sea Grasses, and Benthic Microorganisms
Notes for Marine Biology: Function, Biodiversity,
EcologyBy Jeffrey S. Levinton
©Jeffrey S. Levinton 2001
Seaweeds
1. Usually connect to a substratum2. Take up nutrients from surrounding water3. Need not have the support structures requiredof terrestrial plants
Seaweeds 2
1. Individual seaweed attached to substratumis a thallus, varies from a tarlike crust, to thinsheet, to erect branching forms2. Thallus is often attached to surface by meansof a holdfast3. Stipe is the usually tubular and sturdyStructure that connects holdfast to rest of Thallus4. Flattened section of a thallus is known as ablade
holdfaststipe
blade
(a) (b) (c)
(d)(e)
Variation of form in seaweeds
(a) Ulva sp. (b) Codium fragile(c) Corallina sp. (d) Polysiphonia sp. (e) Laminaria sp.
Seaweeds 3
Seaweed growth:
In smaller seaweeds, can occur nearlyanywhere on thallus
In larger seaweeds, occurs in specializedgrowth areas known as meristems
Seaweeds 4
Seaweed classification
On basis of pigments used in gathering lightfor photosynthesis, by storage products, andby type of flagellae in spores
Seaweeds 5Seaweed Group Photosynthetic
PigmentsStorage
ProductsCell Wall
Green algae Chlor. a, b Starch Cellulose (not all)
Brown algae Chlor. a, c Fucoxanthin
Laminarin Mannitol
Alginate
Red algae Chlor. a, d Phycoerythrin, Phycocynanin
Floridian starch
Agar, Carageenan
Seaweeds 6Seaweeds have complex life cycles:
Haploid (N chromosomes) often alternateswith diploid (2N) phase
Gametophyte produces gametes, released fromgametangia (single cells or more complex structures)
Gametes merge to form zygote --> sporophyte
Seaweeds 7
N
N2N
N
2N
2N
N
N
N
N
N2N
Isomorphic Heteromorphic Single morph. phase
G S G S G
Ulva CodiumLaminaria
G = gametophyte, S = sporophyte
Life history types
Seaweeds 8
Seeweed Groups
Green seaweeds (Chlorophyta)
• Similar photosyn. Pigments to higher plants
• Range of form from one cell to filmy forms such as Ulva to finger shaped Codium
Green seaweed Enteromorpha, with red coralline algae
Brown seaweeds (Phaeophyta)
• Range from small filamentous forms to common seaweeds on the shore such as Fucus, to enormous kelps (e.g. Macrocystis)
• Get color from pigments xanthophyll and carotene
• Contain phycocoloids, alginates, other substances used by people in toothpaste, pills, salad dressing, potash and acetone also extracted from some species
Brown seaweed Fucus sp.
Pacific coast brown seaweed Hedophyllum sessile
Red seaweeds (Rhodophyta)
• Phycoerythrin is the pigment giving them color
• Complex life cycles• Great range of forms, including calcareous
forms common on coral reefs, rocky subtidal reefs
• Carageenan obtained from Irish Moss for material used in cream cheese, ice cream. Agar is extracted from Gracilaria
Coralline algae with chiton
Sea Grasses• Flowering plants, including eel grass Zostera
marina, turtle grass Thalassia testudinum• Flowers are not fancy (no animal pollinators)• Pollen floats along until encountering a
receptive stigma• Seeds move a short distance before setting
and germinating, turtle grass fruit can travel longer distances
Sea grass Phyllospadix
Sea Grasses 2• Usually grow asexually by means of
rhizome system, which extends beneath the sediment surface
• Often have high cellulose content, difficult to graze (eel grass hardly grazed at all)
Benthic Microorganisms
• Occur as single cells or chains of cells, cells can move in sediment pore water
• Skeleton made of silica• Benthic forms dominated by pennate
diatoms• Cell division main form of growth, but
also sexual reproduction• Most occur singly, but some are colonial
Diatoms
Pennate diatoms
Benthic Microorganisms 2
• Occur as single cells or in connected groups
• Crucial in decomposition• Bacterial reproduction through cell
division, genetic exchange between cells possible
• Most are heterotrophic, but there are a wide variety of types, acting on many different substrates
Bacteria
Benthic Microorganisms 3
• Occur free living but also as symbionts with plants and animals
• Photosynthetic but also capable of nitrogen fixation
• Commonly multicellular arranged in cell rows (trichomes), grouped into filaments
• Nitrogen fixation occurs in larger cells, heterocysts
• Blue greens can make resting spores
Blue-Green Bacteria (Cyanobacteria)
Benthic cyanobacteria Lyngbya
Benthic Microorganisms 4
• Very common in marine environment
• Usually heterotrophic, extremely important in decomposition processes of particulate organic matter
Fungi
The End