The Seagrasses Kim Peyton University of Hawaii - Manoa Department of Botany Novel floral adaptations have led to new types of wetlands, wetland functions, and wetland faunal niches. Greb et al. (2006) What is a seagrass? •Submerged Aquatic Vegetation (SAV) •Marine angiosperms •Herbaceous monocots •Functional grouping of plants Outline • Anatomy • Characteristics of seagrasses • Taxonomy & systematics • Evolution of seagrasses • Distribution of seagrasses • Hawaiian seagrasses •Seaggyrass diversity • Habitats • Reproduction • FdFood sources • Annual Production Estimates • Stressors of seagrasses • Ethnobotany Anatomy • Blades - Photosynthesis Nutrient uptake • Short shoot = stem • Rhizomes - Anchoring Propagation Nutrient absorption Gas e xchange • Roots - Nutrient uptake Anchoring Gas exchange Vegetative Morphology • Leaves: strap-like to oval • Leaf bundles • Short shoots Conveyor-belt growth Characteristics of Seagrasses: Functional Group Arbor (1920) & den Hartog (1970) 1. Adapted ecologically to varying salinities = osmoregulation 2. Able to grow while completely submerged (vs. emergent vegetation) 3. Resistant to waves & tidal currents 4. Adapppted to pollinate underwater = hydrophilly 5. Competitive in the marine environment The Ruppia & Lepilaena Problem • 5th seagrass characteristic effectively removes Ruppia & Lepilaena from the seagrass designation • Freshwater - brackish - marine species How extraordinary are seagrasses? How extraordinaryyg are seagrasses? Aquatic angiosperms • 17% of the families • 1. 5% of the genera • 2% of the species But over 100 independent origins are estimated - diversity measured differently How extraordinary are seagrasses? How common is hydrophily? • 130 species of 300,000 species • Hydrophiles = 0.04% • 60 species are marine = seagrasses • Seagrasses = 0.02% How extraordinary are seagrasses? 1. Correlation between marine habitat and hydrophily 2. Reflects difficult evolutionary transitions Where did seagrasses come from? Halophytes SAV - emergent - freshwater Seagrasses rbcL marker (Les etlt al 1998) • 3 lineages • 5 families • 12 genera • SAV ancestry Can you find Ruppia? Distribution of Seagrasses Temperate - Boreal Regions • 4 genera •~ 28 spec ies Tropical - Subtropical Region • 7 genera • ~ 30+ species Eurythermal • Ruppia • ~ 2-10 spp. Facultative successional sequence spans coastal wetlands (mangrove forests), seagrass meadows and coral reefs. Origins of this relationship found in the late Cretaceous with the first appearance of seagrasses and mangroves. (Brasier 1975; McCoy & Heck 1976) The seagrasses of Hawaii Halophila decipiens Halophila hawaiiana Ruppia maritima Tropical wetlands (mangroves) - seagrass meadows - coral reefs: Shared succession coupled with integrated tropic relationships Shared Pan-Tethyan Coastal wetlands (mangroves) - distribution: seagrass meadow- coral reefs • seagrasses • cor al r eef fi sh es • decapods • foraminifera • mollusks • manatees McCoy & Heck 1976; Brasier 1975; Domning et al. 1982 Seagrass Diversity Enhalus Halodule Zostera Posidonia Halophila Phyllospadix Habitats: Soft Sediment Leaves reduce flow Particulate matter drops out Rhizomes - sediment accumulation Roots - stabilization Habitat for infaunal organisms Habitats - Hard Bottom Rocky Inner Tidal Phyllospadix Late su ccessional species Seagrass Fruits & Seeds Bird dispersed Phy llospa dix ZtZostera & Ruppia fruits Large seeds Seed bank •Fruits with hooked barbs •Macroalgae •Roots sticky Turner (1983) Vegetative fragments Seagrass as a food source: Grazers Smaragdia spp. Waterfowl Dugongs & Manatees Green Turtles Seagrass as a food source: suspension & deposit feeders • Few direct grazers (temperate) • Sequestered nutrients • Litter • 10 tons leaves per acre per year • 50 million invertebrate infauna per acre Estimated Annual Production & Bla de Elonga tion Ra te: Flor ida Virnstein (1982) Halodule beaudettei 182 - 730 g C m-2 y-1 ~3.1 mm/d Syringodium filiforme 292 - 1095 g C m-2 y-1 ~8.5 mm/d Thalassia testudinum 329 - 5840 g C m-2 y-1 ~2-5 mm/d Anthropogenic Stressors Sewage discharge Non-point pollution Alga l ep ip hy tes Reduction of PAR Invasive Species Caulerpa taxifolia - cultured strain Mediterranean Sea; California; Australia Posidonia oceanica - endemic seagrass Aquarium dumping Hawaiian flora reflects isolation Background Halophila hawaiiana Limu enenue •Endemic species • 2-3hiht3 cm canopy height • Builds perennial mounds (den Hartog 1970) Depth Distribution: 1-90 ft Halophila decipiens Invasive species and the seagrasses of Hawaii: Disppglacement & Smothering Gracilaria salicornia Gracilaria sp. Florida Halophila decipiens Halophila hawaiiana Ruppia maritima Avrainvillea amadelpha Maunalua Bay - East Honolulu Urbanized watershed WtWater d ep th13th 1.3 m Methods - Removal Experiment Halophila hawaiiana & Avrainvillea amadelpha • Established 25 0.25 m2 fixed plots with 10 treatments, 10 controls with alga & 5 controls without alga • Treatments - Avrainvillea is removed • Quantified % cover and blade pair densities (Morris et al. 2000) • Monitored over 120 days • June 2004 to October 2007 + June 2004 to June 2008 Invasive Removal Results 100 * June 2004 80 * October 2004 January 2005 Cover June 2005 60 October 2005 January 2006 40 June 2006 Percent nn October 2006 20 June 2007 Mea October 2007 0 Seagrass Seagrass Invasive alga Invasive alga Seagrass Invasive alga (Treatment) (Invasive (Treatment) (Invasive (Seagrass (Seagrass Control) Control) Control) Control) Invasive Removal Results 100 * June 2004 80 * October 2004 January 2005 Cover June 2005 60 October 2005 January 2006 40 June 2006 Percent nn October 2006 20 June 2007 Mea October 2007 0 Seagrass Seagrass Invasive alga Invasive alga Seagrass Invasive alga (Treatment) (Invasive (Treatment) (Invasive (Seagrass (Seagrass Control) Control) Control) Control) A line in the sand - in which direction is the invasion going? June 2004 Avrainvillea June 2008 June 2004 Seagrass Sand Blow-out in Seagrass Meadow Limu Sand Blow- out in Seagrass Meadow Natu ral Dist u rbances: Tree fall in a forest Forest fire Land slide Volcanic eruption Waikiki Site Descriptions: Dredged Areas 1 = Impact Site 2 = Control Site • Discontinuous • >3300 m2 continuous meadows of 57 m2 meadow & 21 m2 • 2.5-3.5 m water • Seagrass depth confined to upper 2 • Occasional ppgortions of dredged fragments of G. slope in 2-2.5 m salicornia water depth • G. salicornia Hard bottom tumbleweeds at 3- 3.5 m water depth 1 Gracilaria salicornia - Negative impacts in a Halophila decipiens meadow? The invasive alga Gracilaria salicornia The invasive alga Gracilaria salicornia G. salicornia fragments can grow into tumbleweeds. Results, so far Control Site Impact Site • >3300 m2 • Discontinuous continuous H. meadow of H. decipiens meadow decipiens 57 m2 & 21 m2 • 3-3. 5 m w ater depth • 2-2.5 m water •No G. salicornia depth • Honu feeding area • G. salicornia present 3-3.5 m watdthter depth Seagrass results , so far 9000 8000 7000 6000 5000 af pairs/m2 ee 4000 3000 Mean l Mean 2000 1000 0 Control Impact 100 90 80 70 60 50 40 Mean dry wt/m2 30 20 n=10; n.s. 10 0 Control Impact Seagrass results, so far 4000 3500 22 3000 2500 r of fruits/m 2000 ee 1500 1000 Mean numb 500 0 Control Impact n=10; p<0.00001 Ruppia maritima Bristle-Thighed Curlew flipping matfts of RiRuppia on MlkiMolokai A. Dibben-Young Ruppia is present in some wetlands and absent in others. Why? Experiments Two experiments: •Each at two sites •Both tilapia genera Test for other factors Exclosure experiment n = 6 4 Levels Cage experiment Results CtlControl Large Tilapia Small Tilapia Day 0 Day 0 Day 0 Day 6 Day 6 Day 6 Results: Cage Experiment Large tilapia consume Ruppia 60 50 40 30 eight (g) 20 Tilapia Large WW Tilapia Small 10 Top Minnow Large Top Minnow Small 0 No Fish Control nge Wet aa Treatments -10 % Ch -20 -30 -40 Ethnobotany of Seagrasses • Non-flammable insulation - both thermal & sound-proofing US&UKUS & UK • Roofing thatch - slow to rot & flea proof UK • Binding soils - dikes in the Netherlands & stabilize sand dunes • Stu ffing in p illows, ma ttresses & up ho ls tery Europe & US • Packing material for seafood - Zostera japonica • Rain gear - Phyllospadix - pre-rubber Japan • Hawaii as bait.