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

23

24

25

26

27

28

29

30

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