Chlorophyta (green algae)

Lecture 8

OVERVIEW

Eubacteria & Protists• Cyanophyta• “Phytoplankton”• Chlorophyta, Phaeophyta, Rhodophyta

Vascular Plants (Gymnosperms & Angiosperms)• Seagrasses – Hydrocharitaceae & Potamogetonaceae• Saltmarshes – Poaceae, Juncaceae, etc• Mangroves – Rhizophoraceae, Avicenniaceae• Beach & Dune plants

Fan-Shaped Phylogenetic Tree

“MACRO-ALGAE” = seaweeds

• Divisions:– Chlorophyta (green)– Phaeophyta (brown)– Rhodophyta (red)

• Separated on basis of pigments (color)

• Evolved 900-600 Mio (Cambrian)

• Continental Margins – Rocky shores or lagoons predominantly.

Div Chlorophyta

– Chlorophyta (green) – 900 spp (about 10% of known spp, rest are freshwater).

– Ancestor of terrestrial plants (Kingdom Plantae)

– Chl a + b, (B-carotene, xanthophylls – photoprotective role)

– Uni-nucleate, also Multi-nucleate (siphonous)– 6 Orders: e.g. Ulvales, Cladophorales,

Caulerpales– Cosmopolitan and tropicals

Algal pigments

Pigment Molecules

CHLOROPHYLL CAROTENES

Epiphytes

Cladophora

Enteromorpha

Chaetomorpha

Ulva Enteromorpha

Halimeda Caulerpa

THALLUS

SHEET

COARSLEY - BRANCHED

JOINTED -CALCAREOUS

THICK -LEATHERY

FILAMENT

ENCRUSTING

Form - Function

Incr productivity

Ulva Enteromorpha

Halimeda Caulerpa

Why simple = more productive?

• Nutrient uptake, waste removal in single cell relies on diffusion, some active uptake.

• No translocation within plant necessary

• Reduce boundary layer effects – promotes diffusion into cell.

• No metabolic losses to structural tissues

• Faster life-cycle (hrs – days)

Boundary Layers

• Zone of little-no flow around an object/surface.

• Inhibits diffusion• Movement promotes

flow past object, breaking down boundary layer

• Important for algal nutrient and CO2 uptake

Boundary Layers

• Zone of little-no flow around an object/surface.

• Inhibits diffusion• Movement promotes

flow past object, breaking down boundary layer

• Important for algal nutrient and CO2 uptake

Diffusion across cells/membranes

Simple Structure and Succession

• r vs K selected life-strategies

• r = Ulva, Enteromorpha• K = Halimeda, Penicillus• Taxonomy generally

from simple to complex:single cells, filaments, multi-filament, corticated,specialized structures

Chlorophyte taxonomy

• Number of classes has increased from 1 in 1903, to 3 in 1990, to 10 in 1995.

• Based on EM (2 types of cell division, flagellum ultrastructure) and RNA sequence in chloroplast and mitrochondria, DNA in nuclei.

• Ancestors of terrestrial vascular plants• Class Prasinophyceae – single cell (plankton).• Class Chlorophyceae – 6 of 15 orders have

seaweeds.

Thallus organization

• Unicell flagellate – Chlamydomonas

• Colonial flag – Volvox

• Tetrasporal, Coccoid, Sarcinoid groups

• Filamentous – Ulothrix

• Thallose – Ulva

• Siphonous - Caulerpa

Evolution

Chlamydomonas

VOLVOX

Spyrogyra

Chara - muskgrass

Chlorophyceae taxonomy (recent)

• Or. Ulvales (Ulotrichales) – Fam. Ulvaceae + 5 others

• Cladophorales – Cladophoraceae + Anadyomenaceae

• Acrosiphoniales – 1 order• Siphonocladales – Siphonocladaceae,

Boodleaceae, Valoniaceae• Caulerpales – Bryopsidaceae, Caulerpaceae,

Codiaceae, Udoteaceae, + 2 others (FW)• Dasycladales – Dasycladaceae +

Acetabulariaceae

Cl. Chlorophyceae taxonomy

Dawes, pg 122

Or. Ulvales

Ulva

Or. UlvalesEnteromorpha

Or. Cladophorales

Cladophora

Or. Cladophorales

Anadyomene

Or. Siphonocladales

Boodlea

Siphonocladus

Or. Siphonocladales

Holdfast

Valonia

Or. Caulerpales

Or. Caulerpales

Or. Caulerpales

Caulerpa mexicana

Or. Caulerpales

Or. Caulerpales

Codium

Or. Caulerpales - rhizophytic

“root-ball”

Or. Caulerpales

Or. Caulerpales

Halimeda

Or. Dasycladales

Dasycladus

Batophora

Or. Dasycladales

Acetabularia

MS Chlorophyta (1957)

• Ulvales – Enteromorpha flexuosa, E. lingulata, E. plumosa, Ulva lactuca– Ulotrichaceae – Stichooccus marinus– Chaetophoraceae – Entocladia viridis,

Phaeophila floridaerum, Ulvella lens

• Cladophorales – Cladophora fascicularis, C gracilis, Rhizoclonium riparium.

• Siphonales – Osterobium queketti• about 12 species…

Chlorophyta in the “news”• Ulva and Enteromorpha abundance increases in Baltic

Sea / Adriatic Sea due to eutrophication – smothering seagrass and mudflats, smelly wrack driving tourists from beaches.

• Enteromorpha bloom in China largest ever recorded – thought to originate from aquaculture.

• Caulerpa taxifolia – Killer Algae escapes Monaco aquarium. Covers 10’000acres in Med within <10years.

• Halimeda and Dictyota (brown) smother Fla Keys reef tract – response to eutrophication from septic systems?

• Acetabularia used in studies of abiotic and genetic cues for algal development.

Chlorophyta in the “news”• Ulva and Enteromorpha abundance

increases in Baltic Sea / Adriatic Sea due to eutrophication – smothering seagrass and mudflats, smelly wrack driving tourists from beaches.

Enteromorpha bloom seen from space! (Liu et al. 2009)

Enteromorpha bloom seen from space! (Liu et al. 2009)

Cause: more aquaculture of seaweed (Porphyra) forsushi. Green algae a by-product. Ocean circulationmoved bloom of green algae north and east, so accumulatesonshore far from source population.

Chlorophyta in the “news”• Caulerpa taxifolia – Killer Algae escapes

Monaco aquarium. Covers 10’000acres in Med within <10years.

http://aquat1.ifas.ufl.edu/seagrant/cautax2.html

Chlorophyta in the “news”• Halimeda and Dictyota (brown) smother Fla

Keys reef tract – response to eutrophication from septic systems?

Orange Bay, Jamaica. Eutrophication from sugar cane fields

SAND KEY, FLA

Chlorophyta in the “news”• Acetabularia used in studies of abiotic and

genetic cues for algal development.

Chlorophyta and Coral reefs

Coral Reefs

Acropora - staghorn Porites – finger coral

Acropora - Elkhorn Montastrea – boulder coral

Global Distn

Reef Zonation

LagoonBack-reefReef flatRimSpur-and-

grooveSlope

Deep plain

GBR – Heron Island

Reef Plant-Animal interactions• "The Living Coral Reef is one of the most diverse and complex

communities in the world".• The Florida Keys coral reef community presents approximately 107

species of corals (over 80% of all coral species of the tropical Atlantic) and over 500 species of tropical fish.

• The interaction and interdependence among all these organisms is so critical that many reef inhabitants cannot live outside the reef zone (e.g. Grunts).

• Sunlight, water, fish, invertebrates and plants play major roles in the sustaining and building of the reef: – Sunlight --> Photosynthesis. – Water --> Brings nutrients, O2, CO2. – Fish --> Excrements help build and cement reef. – Invertebrates and Plants --> Secrete calcium carbonate sediments that

cement reef; food source; also graze the reef algae, creating space for corals to get established and grow.

http://www.reefrelief.org/ecosystem.html

Reef formation

• Fringing reefs – Fla Keys

• Barrier Reefs – GBR, Belize

• Atoll reefs – Pac volcanic islands

Reefs in peril

1960’s

2000’s

In <40 ysmore than 50% of reefs have declined globally!!!!!

Importance of herbivores: fish, urchins, snails

Lytechinus die-off Caribbean-wide in 1983 results in macroalgal blooms on reefs

Bottom-up Vs Top-down

• Coral dominance under low nutrient, high grazer abundance.

• Algal dominance under high nutrient and/or low grazing.

• Bottom-up = eutrophication. Algae out-grow corals and smother recruits.

• Top-down = overfishing of large fish predators AND herbivores. Trophic cascade, results in too few micrograzers to check algal growth.

Seen this before in seagrasses – remember Heck and Valentine 2006paper?

Summary

• Chlorophyta – ancestors of vascular plants

• 10% marine, high tropical diversity

• Unicell -> Filamentous -> Siphonous

• Ulva, Enteromorpha cosmopolitan indicators of eutrophication

• Coral reef algae and “alternate stable states”: eutrophication vs trophic cascade