Mangals & Salt Marshes- Vascular Plant Tidal Communities Switching gears from algae to angiosperms Low energy coastal regions such as estuaries or coastal habitats protected by barrier islands holdfast blade flower leaves stem Less tissue specialization Happy in salt water roots/rhizomes More tissue specialization Stressed by salt water 1 2 Types of flowering plants Zonation Patterns- physical factors and biotic interactions 1. Mesophytes/ Glycophytes- grow where freshwater is available & lack specialized adaptations that prevent water loss 2. Hydrophytes- live in water, partially or fully submerged (seagrass) 3. Xerophytes- have, morphological, anatomical, & reproductive adaptations to aid in the retention of water ( mangroves & salt marsh plants) 1. Halophytes- adaptations to prevent water loss & can grow in saline habitats 1. Facultative- do not require saline conditions 2. Obligate- specific requirement for sodium to complete their life cycle 3 1
Zonation Patterns physical factors biotic interactions Salt Marshes -typically areas of natural salttolerant herbs, grasses, or low shrubs growing on unconsolidated sediments bordering saline water bodies whose water levels fluctuates tidally Over 400 species- 9 maritime formation biotic interactions physical factors Dave Lohse 6 Salt Marsh Zonation Salt water flooding Sarcocornia Distichlis Spartina Graciliaria Zostera salinity Juncus + Relatively high nutrients - detritus - Soil anoxia - Hypersaline to evaporation - Disturbance from beach wrack Land 7 Some adaptations for salt marsh living: Salt stress Epidermal salt glands Salt vacuoles store salt in stem, drop stems seasonally Thick cuticle reduce contact Succulent Soil anoxia: Aerenchyma = tissue with air spaces Lacunae = space in stem to root 8 2
Some adaptations for salt marsh living: Soil Anoxia & Substrate Type: Rhizomes- thick anchoring & delicate absorbing roots, bind unconsolidated sediments to reduce erosion, release oxygen reduce anaerobic conditions suppress methane production Ecological Roles of Salt Marshes 1. Primary Production- below ground biomass 90%, 10 x sequestration rates of terrestrial forest, 90% in soil so long term blue carbon storage 2. Food Sources- detrital food chain 3. Habitats-important nursery habitats for marine fish 4. Stabilization of Sediments- root systems 5. Filtration- removal of organic waste by marshes lowers the sediment and nutrient loading to adjacent shores 9 10 Blue Carbon- carbon sequestration in coastal ecosystems, mangroves, salt marshes & seagrass beds Even though global area is 1-2 orders of magnitude smaller than terrestrial forests, contribution to carbon sequestration per unit area of coastal ecosystems is much greater McLoed et al 2011 11 12 3
Salt Marshes & Climate Change- Sacramento- San Joaquin Delta 750,000 acre vast and complex wetland Levee construction & land drainage changed this to farmland Drinking water to 25 million people & irrigation of 3 million acres of farmland Spartina foliosa native cord grass This has released 0.9 billion tco2, land subsides 1.5 inches a year releasing 22tCO2 per acre Conservation Carbon Farming on Twitchell Island restore native tules & cattails on 15 acre plot plan for 2,500 acres by 2017 costing $5,000 per acre Greenhouse gas benefits 14 tco2 per acre per year soil accretion of more than an inch per year Reduce cost of levee maintenance & lower risk of levee failure Monocot in the grass family- Poaceace 3m tall culms (stems) Culms & leaves only 1/3 to 1/10 of biomass Salt glands excrete excess salt, leave salt crystals on leaves Have lacunae tissue in stems/roots allows oxygen transport to roots (often aneorobic soil) Occur in lowest parts of salt marsh 13 14 Spartina foliosa/alterniflora HYBRID Problem in salt marsh communities in the SF Bay & Puget Sound Negative impacts: Changes physical environment (oxygen, nutrients, hydrology, accretion rates) Displaces native cordgrass (S. foliosa) and pickleweed Changes invertebrate community (much less rich) Decreases available water chokes water channels, decreases foraging area for birds Eradication is difficult Grosholz lab, UC Davis 15 Sarcocornia pacifica pickle weed Dicot-Chenopodiaceae Succulent- water containing cells Concentrates salt in tissues, drops stems every year Often parasitized by dodder, Cuscuta salina Occurs in the low-mid marsh 16 4
Distichlis sp, the salt grass Has salt glands Occurs in the high marsh East coast: An experiment examining the effects of salt stress on species interactions: (Bertness and Shumway 1993, AmNat) Positive interaction = Facilitation Negative interaction = Competition Juncus spp, the spiny rush Occurs in the high marsh Research question: Is the nature of species interactions mediated by the physical environment? 17 18 The players: Spartina zone gets flooded more, less saline Juncus zone becomes hypersaline thru evaporation Distichlis co-occurs with both Spartina and Juncus The experiment: Remove all vegetation in plots of both zones Remove neighbors (potential competitors or facilitators) in half of plots Water (alleviates salt stress) in half of plots Count percent cover of target species, see whether target species increases or decreases based on neighbors and physical stress Distichlis Juncus Spartina Bertness and Shumway 1993, AmNat 19 Spartina Juncus Bertness and Shumway 1993, AmNat 20 5
The experiment: Remove all vegetation in plots of both zones Remove neighbors (potential competitors or facilitators) in half of plots Water (alleviates salt stress) in half of plots Count percent cover of target species, see whether target species increases or decreases based on neighbors and physical stress Juncus Treatments in each zone: -Water + Neighbor - Water - Neighbor Control + Water + Neighbor Watered + Water - Neighbor The results: Spartina zone (less Spartina outcompetes Distichlis in both watered and control plots Distichlis more abundant when neighbors are removed. Juncus zone (more Spartina Bertness and Shumway 1993, AmNat A FACTORIAL DESIGN 21 modified from Bertness and Shumway 1993, AmNat 22 The results: Spartina zone (less Spartina outcompetes Distichlis in both watered and control plots Distichlis more abundant when neighbors are removed. Competition is prevailing interaction The results: Spartina zone (less Spartina outcompetes Distichlis in both watered and control plots Distichlis more abundant when neighbors are removed. Competition is prevailing interaction Juncus zone (more Juncus zone (more Control plots presence of neighbors increased abundance of Juncus = facilitation modified from Bertness and Shumway 1993, AmNat 23 modified from Bertness and Shumway 1993, AmNat 24 6
The results: Spartina zone (less Spartina outcompetes Distichlis in both watered and control plots Distichlis more abundant when neighbors are removed Competition is prevailing interaction Juncus zone (more Control plots presence of neighbors increased abundance of Juncus = facilitation The conclusion: Alleviating salt stress shifts nature of interactions from facilitative to competitive Bertness and Shumway 1993, AmNat ction Negative interac ns Positive interaction Associational defenses Physical stress Neighborhood habitat amelioration modified from Bertness and Shumway 1993 Watered plots Neighbors decrease abundance of Distichlis 25 = competition Consumer pressure 26 modified from Bertness and Callaway 1994,TREE Mangals Mangal taxonomy Domain Eukaryote Kingdom/Clade Plantae Phylum/Division Magnoliophyta -angiosperms Class Magnoliopsida Order Malpighiales Family Rhizophoracea Genus Rhizopora species mangle- red mangrove Mangroves & associated tidal marsh communities 27 28 7
Mangal Distribution Mangal Genera Share the following features: 1. Species restricted to mangals. 2. Trees exhibit major role in community structure. 3. Morphological specializations, including aerial roots & vivipary 4. Plants exhibit salt- exclusion physiology 5. Taxonomic isolation from terrestrial relatives at the level of genera - Tropical tidal habitats - 40 species of Mangroves dominate 75% of the tropical coastline between 25 N & 25 S - Orders Myrtales & Rhizophrales make up 50% of the species 29 30 Mangrove Forest Classification 1 Coastal Fringe- along protected shoreline berms 2 Overwash- low intertidal 3 Riverine- along streams and rivers and extend several miles inland 4 Basin- occur in a depression behind a berm or fringing mangals, connected to streams or tidal creeks 5 Scrub- occur where abiotic conditions are severe due to limited water 6 Hammock- inland tropical wetlands, isolated by fresh water 31 32 8
Adaptations of Mangroves Mangrove Leaves 1. Mechanical adaptations for attachment in soft sediment 2. Aerial roots are common & specialized for diffusion of gases to subterranean portions. 3. Vivipary- germination of seedlings while fruit remains attached to tree 4. Seeds & seedlings can survive in salt water & disperse via salt water 5. Xerophytic modifications- survive with little fresh water 6. Halophytic modifications- survive with high amounts of 33 salt evergreen complex leaf anatomy thick outer walls & cuticles salt is accumulated in leaves causing succulence and eventually shed glandular hairs- function in salt excretion lenticles- cork warts secrete water & chloride hypodermis upper layer contains tannins lower layer contain hydrocytes- water containing cells 34 Mangrove trunks & bark lenticles- dense masses of cells that results in breaks in the bark - function in gas exchange - critical for root survival 40% of root is used for gas exchange 35 36 9
Zonation patterns Rhizopora mangle- red mangrove Red Bark & Leathery Leaves Vivipary-seedling germinate from fruit while attached to tree Upper limit determined by biotic interactions Lower limit determined by abiotic factors Stilt roots- develop from the stem prop - develop from a branch drop Lacunae- gas exchange 37 38 Lacunae- gas exchange Avicennia germinans- black mangrove Hair on leaves- salt secretion Cryptovivipary-embryo grows out of the seed but not the fruit before dropping Enlargement of airspaces Air spaces forming channels in leaves, stems and roots Also have a structural role 39 Aerenchyma tissue- gas exchange Cable root with Pneumatophores- extend 10-20 cm above root function in gas exchange 40 10
Aerenchyma tissue- gas exchange Avicennia marina- white mangrove Formed by cell separation Mechanism for root aeration in low oxygen concentrations Stilt or Cable roots 41 Nectaries at base of leaves secrete sugar Hair on leaves- salt secretion 42 Mangal Macroalgae important primary producers epiphytic algae on roots = to the leaf litter from the tree Water Regulation & Osmoregulation facultative halophytes- competitive exclusion limits them to saline habitats slow growth because they spend a lot of energy dealing with salt salt secretors- Avicennia- 33% of the salt non secretors- Rhizophora - exclude 90% of salt 43 44 11
Ecological roles of Mangals 1. Coastal Resilience 2. Filtering land runoff 3. Stabilization of sediments 4. Trapping sediments 5. Primary Production 6. Nursery Habitats Coastal Resilience & Mangroves Storm surge- low pressure & high winds raise water level at the coast -peak water levels can exceed 7m in height flooding Mangroves can reduce storm surge and surface waves 45 46 Loss of Mangals extraction, pollution & reclimation Blue Carbon- carbon sequestration in coastal ecosystems, mangroves, salt marshes & seagrass beds Has lead to declines of finfish & commercial shrimp these species depend on detrital & benthic microalgae Long term pollution from oil spills cause mutations in the trees Habitat Loss seagrass 1.5% yr mangroves 1.8% yr tropical forests 0.5% yr 47 Even though global area is 1-2 orders of magnitude smaller than terrestrial forests, contribution to carbon sequestration per unit area of coastal ecosystems is much greater McLoed et al 2011 48 12