synopsis on seagrass of egypt, seagrass morphology and general taxonomy
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Synopsis on Seagrass of Egypt, Seagrass Morphology and General Taxo
nomy
Dr. Soha ShabakaHydrobiology Laboratory
National Institute of Oceanography and Fisheries Ministry of State for Scientific Research of Egypt
I- Introduction
Evolutionary history of seagrasses
Land plants penetrating into the sea and not well developed
Well-adapted seagrasses with some terrestrial characteristics.
Modern seagrasses.
Seagrasses should posses the fol
lowing criteria (Arber 1920) :
1. Adapted to live in a saline medium
2. Grow when completely submerged
3. Strong anchoring system
4. Capacity for hydophilous pollination
What are seagrasses?
Marine plants with the same basic structure as terrestrial (land) plants.
They are quite different from seaweeds.
Algae (Ulva lactuca) Seagrass
Schematic illustration of major human-induced impacts on a tropical seagrass ecosystem. (Duffy J. E. 2006).
Seagrass deterioration (Orth et al., 2006)
Extreme events (Hurricanes and Tsunamis) Global warming Invasive species Overgrazing Algal blooms Wasting disease Sediment and nutrients runoff (low water quality) Commercial fishing operation Aquaculture
General Taxonomy
Division: Magnoliophyta (Angiosperms) Class: Liliopsida (Monocotyledonus)
Seagrasses are grouped into 12 genera, to which belong about 60 species.
Families: Zosteraceae (Zostera, Heterozostera, Phyllospadix), Posidoniaceae (Posidonia), Cymodoceaceae (Cymodocea, Halodule, Thalassodendron, Syringodiu
m, Amphibolis) Hydrocharitaceae (Halophila, Thalassia, Enhalus). Ruppiaceae Potamogetonaceae
II. Seagrass of Egypt
a. Mediterranean Sea (8 species)
Zosteraceae (Zostera),
Posidoniaceae (Posidonia),
Cymodoceaceae (Cymodocea, Halodule),
Hydrocharitaceae (Halophila).
Ruppiaceae (Ruppia)
Potamogetonaceae (Potamogeton)
Posidonia oceanica
Cymodocea nodosa
Zostera noltiiZostera marina
Ruppia cirrhosa
Halodule uninervisHalophila stipulacea
Potamogeton pectinatus
Seagrass distribution in the Mediterranean Sea coast of Egypt (Aleem 1962, 1955, Lipkin 1977, Vitiello et al. 1985, Mostafa 1991, 2006, Shabaka 2004)
Posidonia oceanica
Cymodocea nodosa
Zostera marina
Zostera noltii
Posidonia oceanica
Cymodocea nodosa
Halophila stipulaceae
Posidonia oceanica
Halophila stipulacea?
Situation in 1950-1980Situation in 1990 till early 2000Present situation
?
Posidonia oceanica
Cymodocea nodosa
Halophila stipulaceae
Seagrass distribution in the northern lakes of Egypt
Ruppia cirrhosa,
Cymodocea nodosa,
Halodule uninervis,
Halophila stipulacea,
Potamogeton pectinatus
Zostera marina
Potamogeton pectinatus
b. Red Sea (9 species)
Cymodoceaceae (Cymodocea, Halodule, Thalassodendron, Syringodium),
Hydrocharitaceae (Halophila, Thalassia).
Halophila stipulacea
Halophila ovalis
Halodule uninervis
Thalassia hemprich
ii
Thalassodendron ciliatum
Syringodium isoetifolium.
Halophila decipiens
Cymodocea serrulata
Cymodocea rotundata
Halophila stipulaceae
Halophila ovalis
Halodule uninervis
Thalassia hemprichii
Present situation
None
Seagrass distribution in the Suez Canal lake El-Temsah and Bitter Lakes of Egypt (Aleem 1980)
30 31 32 33 34 35 36 3721
22
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T aba
S u ez
D ah ab
E in S ou kh n a
R as G h arib
S h a la tin
R as B an as
S afaga
Q u seir
M arsa A lam
W adi E lG em al
H alayeb
H u rgh ada
H alo p h ila stip u laceaH alo p h ila ov a lisH a lo d u le u n iv erv isT h a lassia h em p rich iiT h a lla ssod en d ro n c ilia tu mS yrin g od iu m isoetifo liu m
R as M oh am ed
S h arm E lS h iek
Distribution of seagrass Distribution of seagrass inin the Egyptian Red Sea Coast (after Geneid the Egyptian Red Sea Coast (after Geneid 2004).2004).
Cymodocea serrulata and C. rotundata were collected from El-Suweis (Lipkin 1975)
III. Seagrass morphology and general taxonomy
Morphology of a seagrass unit
Seagrasses can be grouped into 3 main morphological categories:
Strap shaped leaves growing at the top of distinct erect stem
(Thalassia of Hydrocharitaceae and all Cymodoceaceae)
Strap shaped leaves but with very small erect stems
(Enhalus of Hydrocharitaceae, Posidoniaceae and Zosteraceae)
A pair of petiolate leaves at the rhizome nodes
Halophila
Key for seagrass genera
Leaves ligulate Zosteraceae, Posidoniaceae, Cymodoceaceae
leaves without ligula (Hydrocharitaceae)Halophila, Thalassia, Enhalus
Key for seagrass genera
Leaves with numerous tannin cells (Posidoniaceae, Cymodoceaceae)
Rhizome monopodial, herbaceous, with short lateral shoots, leaf sheath persistence more than the leaves
(Posidonia, syringodium, Halodule, Cymodocea)
Rhizome sympodial, woody, with elongate erect shoots
leaf blade shed with its sheath
(Thalassodendron, Amphibolis)
Leaves without tannin cells (Zosteraceae)
Syringodium isoetifolium.
Key for seagrass genera Rhizomes are very thick (Posidonia)
Rhizomes are thin (Cymodocea, Halodule, Syringodium)
Posidonia oceanica
Syringodium isoetifolium.
Halodule uninervisCymodocea serrulata
Key for seagrass genera
Leaves with numerous tannin cells (Posidoniaceae, Cymodoceaceae)
Rhizome monopodial, herbaceous, with short lateral shoots, leaf sheath persistence more than the leaves (Posidonia, syringodium, Halodule, Cymodocea)
Rhizome sympodial, woody, with elongate erect shoots leaf blade shed with its sheath (Thalassodendron, Amphibolis)
Leaves without tannin cells (Zosteraceae)
Key for seagrass genera
leaves with numerous tannin cells (Posidoniaceae, Cymodoceaceae)
Rhizome monopodial, herbaceous, with short lateral shoots, leaf sheath persistence more than the leaves
(Posidonia, syringodium, Halodule, Cymodocea)
Rhizome sympodial, woody, with elongate erect shoots leaf blade shed with its sheath (Thalassodendron, Amphibolis)
leaves without tannin cells (Zosteraceae)
Thalassodendron ciliatum Amphibolis antarctica
After Den Hartog (1970)
Key for seagrass genera
Leaves with numerous tannin cells (Posidoniaceae, Cymodoceaceae)
Rhizome monopodial, herbaceous, with short lateral shoots, leaf sheath persistence more than the leaves (Posidonia, syringodium, Halodule, Cymodocea)
Rhizome sympodial, woody, with elongate erect shoots leaf blade shed with its sheath (Thalassodendron, Amphibolis)
Leaves without tannin cells (Zosteraceae)
Key for seagrass genera
Rhizomes monopodial, herbaceous, with a short lateral shoot at each node Zostera, Phyllospadix
Rhizomes sympodial, lignious, with two roots at each node and a stem that carries one leaf at each node. Heterozostera
Zostera marina Pyllospadix torreyi
Heterozostera tasmanica
Key for seagrass genera
Leaves ligulate Zosteraceae, Posidoniaceae, Cymodoceaceae
Leaves without ligula (Hydrocharitaceae)Halophila, Thalassia, Enhalus
Enhalus acoroides Thalassia hemprichii Halophila ovalis
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