Coastal Ecosystems Dr. Mark A. McGinleyHonors College and Department of Biological Sciences Texas Tech University
Two Main Coastal Environments• Estuarine – Freshwater and sea water meet • Temperate- salt marshes • tropics- mangroves – Intertidal zone • Mudflats • Sandy beaches • Rocky intertidal
Intertidal Zones• Dominated by gradients in two physical conditions – Wave exposure – Tidal exposure
Wave Exposure• Energy in waves can influence – Particle size – Ability of organisms to remain attached to substrate
Tidal Exposure Gradient• Vertical gradient – Higher areas have longer exposure to air than lower areas• Exposure to air can have two negative effects for marine organisms – Desiccation • water loss – Thermal stress • Getting two hot
A Bit of Basic Geology Particle Size Aggregate name Size range Size range scale (Wentworth Other names (metric) (approx. inches) Class)−8 < 256 mm < 10.1 in < Boulder−6 to −8 64–256 mm 2.5–10.1 in Cobble Very−5 to −6 32–64 mm 1.26–2.5 in Pebble coarse grave;l−4 to −5 16–32 mm 0.63–1.26 in Coarse gravel Pebble−3 to −4 8–16 mm 0.31–0.63 in Medium gravel Pebble−2 to −3 4–8 mm 0.157–0.31 in Fine gravel Pebble−1 to −2 2–4 mm 0.079–0.157 in Very fine gravel Granule0 to −1 1–2 mm 0.039–0.079 in Very coarse sand1 to 0 ½–1 mm 0.020–0.039 in Coarse sand2 to 1 ¼–½ mm 0.010–0.020 in Medium sand3 to 2 125–250 µm 0.0049–0.010 in Fine sand 0.0025–0.00494 to 3 62.5–125 µm Very fine sand in 3.90625– 0.00015–0.00258 to 4 Silt Mud 62.5 µm in>8 < 3.90625 µm < 0.00015 in Clay Mud> 10 < 1 µm < 0.000039 in Colloid Mud
Wave Energy and Shore Particle Size• Larger particles require more energy to move them than smaller particles• Thus, the size of particles on the shore is influenced by the energy in the waves striking the shore• High energy shores contain larger particles than low energy shores
Rocky Shore• Rocky intertidal zone dominated by daily rise and fall of tides – Littoral zone • Part of the time covered by water and part of the day exposed to air• Species living in littoral zone must face the problems with living in both marine and terrestrial habitats
Rocky Shore- Physical Environment• Two dominant gradients in physical conditions – 1) Wave exposure – 2) Tidal exposure • Vertical gradient – Higher areas spend more time exposed to air than lower areas• Exposure to air can have two negative effects – Desiccation – Thermal stress
What Causes These Zonation Patterns?• The field of ecology is interested in understanding the factors that influence the distribution and abundance of organisms• Determined by abiotic and biotic factors
Rocky Intertidal Zone• Rocky intertidal zones proved to be ideal natural labs for studying ecology – Steep vertical gradients – Variable physical conditions – Mostly sessile or sedentary organisms – Small organisms with high density – Easily manipulated
Connell’s Experiments With Barnacles• What causes pattern of zonation? – Physical factors or biotic interactions• Physical Factors – Higher regions exposed to air for longer periods • Thus greater desiccation – Lower regions exposed to air for shorter period of times
Question• Can the barnacles tolerate the environmental conditions outside of the zone where they are found? – Too dry higher up and too wet lower down???
Question• Is the distribution of the barnacles influenced by biotic interactions? – Competition, predation• Could they live higher and lower on the shore in the absence of other species?
Manipulative Experiments• Connell (and others scientists including Bob Paine who also worked in rocky intertidal ecosystems) recognized the importance of manipulative experiments in the field.• Helped move ecology from a descriptive science to an experimental science
Need to Design an Experiment• What experiments would you suggest to try to determine the importance of abiotic and biotic factors on the distribution of these barnacles?• What factors can limit distribution? – Never got there – Can’t live there because of abiotic conditions – Can’t live there because of biotic interactions
Questions• As we talked about in lab, you need to start by asking a question.• Let’s start by thinking about the cause of the boundary between Balanus and Chthamalus – Q. 1. Is Balanus missing form the upper zone because it has never reached there?
Experiment• Place Balanus in the Chthamalus zone and see if it can survive. Make sure that there are no potential competitors or predators affecting them – Control- move Balanus to the Balanus zone – These barnacles are attached to the rocks, so Connell was able to move the organisms around by chipping off pieces of the rock and attaching them elsewhere on the rocks
Results• Balanus did not survive in the higher zone• Conclude- Balanus not living in the upper zone because they can not deal with the abiotic conditions. – Hypothesis- too dry in the upper zone – What experiment could we do to test this?
Questions• Q. 2. Is Chthamalus lacking from the lower zone because it has never dispersed there?• Experiment- move Chthamalus to the Balanus zone with no potential competitors or predators
Results• Chthamalus was able to grow in the lower zone – Thus, not limited by lack of dispersal or by abiotic conditions – Hypothesis- Chthamalus limited by competition for space by Balanus • Test by moving Chthamalus to the lower level and allowing it to interact with Balanus
Results• Chthamalus could not live in the lower zone when Balanus was there – Competitively excluded by Balanus
Rocky Intertidal• Patterns – Biomass and species richness increase closer to the sea
Tide Pools• Pools of water may become isolated and hold water for periods ranging from hours to several days• When pools isolated – Water evaporates – Salinity increases – Temperature increases• Pools can fill during rains – Salinity decreases – Temperatures decrease
Mangroves• Mangroves include a number of tropical trees and shrubs that are able to live in the intertidal zone along tropical coastlines.• Have adaptations to allow them to live in periodically flooded regions with high salt content.• Approximately 70 species of mangrove plants come from 20 different plant families
Problems Facing Mangroves• The soil is very fine and water logged, it is difficult for the root system to support the plant.• Because the roots zone is waterlogged, plant roots are unable to pick up the oxygen they need through the soil.• Because they are living in the intertidal zone mangrove plants have to be able to live in water with high salt concentrations.• No oxygen in the saturated soil.
Importance of Mangrove Ecosystems• serve as nurseries for a number of marine fish and invertebrates. – juveniles of many species hide out among the mangrove roots until they are large enough to move out to the reef.• Second, the mangrove roots protects the shore from the effects of storms and tsunamis. – It has been well documented that parts of SE Asia that were protected by mangroves were much less negatively affected by the big tsunami than those regions where the mangroves have been removed.