Synopsis on Seagrass of Egypt, Seagrass Morphology and General Taxonomy Dr. Soha Shabaka Hydrobiology Laboratory National Institute of Oceanography and Fisheries Ministry of State for Scientific Research of Egypt

I- Introduction

Evolutionary history of seagrasses 　　Seagrasses should posses the following criteria (Arber 1920) : Adapted to live in a saline medium Grow when completely submerged Strong anchoring system Capacity for hydophilous pollination Land plants penetrating into the sea and not well developed Well-adapted seagrasses with some terrestrial characteristics. Modern seagrasses.

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, Syringodium, 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)

Potamogeton pectinatus Zostera marina Zostera noltii Posidonia oceanica Cymodocea nodosa Halodule uninervis Halophila stipulacea Ruppia cirrhosa Potamogeton pectinatus

? ? Present situation Situation in 1990 till early 2000 Posidonia oceanica Cymodocea nodosa Zostera marina Zostera noltii Posidonia oceanica Cymodocea nodosa Halophila stipulaceae Posidonia oceanica Cymodocea nodosa Halophila stipulaceae Posidonia oceanica Halophila stipulacea ? ? Present situation Situation in 1990 till early 2000 Situation in 1950-1980 　　Seagrass distribution in the Mediterranean Sea coast of Egypt (Aleem 1962, 1955, Lipkin 1977, Vitiello et al. 1985, Mostafa 1991,　2006, Shabaka 2004)

Seagrass distribution in the northern lakes of Egypt Potamogeton pectinatus Ruppia cirrhosa, Cymodocea nodosa, Halodule uninervis, Halophila stipulacea, Potamogeton pectinatus Zostera marina Seagrass distribution in the northern lakes of Egypt

b. Red Sea (9 species) Cymodoceaceae (Cymodocea, Halodule, Thalassodendron, Syringodium), Hydrocharitaceae (Halophila, Thalassia).

Syringodium isoetifolium. Thalassodendron ciliatum Cymodocea serrulata Cymodocea rotundata Halodule uninervis Syringodium isoetifolium. Thalassodendron ciliatum Halophila decipiens Halophila ovalis Thalassia hemprichii Halophila stipulacea

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)

Cymodocea serrulata and C Cymodocea serrulata and C. rotundata were collected from El-Suweis (Lipkin 1975) Distribution of seagrass in the Egyptian Red Sea Coast (after Geneid 2004).

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 Posidonia oceanica Rhizomes are very thick (Posidonia) Rhizomes are thin (Cymodocea, Halodule, Syringodium) Syringodium isoetifolium. Halodule uninervis Cymodocea 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 Pyllospadix torreyi Zostera marina 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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