Transcript Chapter 11
Between the Tides http://video.google.com/videosearch?q=Grunion%20run%20at%20la %20jolla&rls=com.microsoft:en-us&oe=UTF8&startIndex=&startPage=1&um=1&hl=en&ie=UTF8&sa=N&tab=iv# La Jolla Grunion Run Where? • Shoreline between high and low tide marks Organismal adaptations? • Community has to be adapted to exposure to air • Communities differ greatly depending on structure – Rocky or sandy bottoms Fig. 11.2 What is the greatest concern to the intertidal organisms? • Water loss or desiccation • Take advantage of crevices, clustering, shade, tidepools, other organisms, etc. Fig. 11.3 Fig. 11.4 • Move to moisture & clamp their ventral surface to the substrate to conserve water (chitons) • Closed mussel shells • Contracted anemone • Resilient tissues that can withstand 75-90% water loss …tidal exposure limits activities …can be harsh conditions Fig. 11.5 Fig. 11.7 Wave exposure and wave shock • Adaptations to cope? – Seaweeds? – Mussels? – Intertidal fishes? • Wave energy varies – – – – Sheltered coastlines Angled wave approach Varied impact to organisms Gradient of impact (shock) and exposure Fig. 11.8 Fig. 11.11 • Distribution, diversity, & abundance partially defined by exposure • Why the differences? Fig. 11.12 • Sheltered – Less wave force – Higher profile • Heavier wave action – Lower profile to reduce drag Fig. 11.13 • Flexibility to deal with wave action Fig. 11.14 • Safety in numbers – (a) Wave force can detach higher profile individuals – Clustering can protect from wave shock (as well as preventing excessive desiccation). – (b) Wave force is indirect – reduced or dissipated some – (c) Too dense can be a problem sometimes • Shaping the intertidal zones so far… – Effects of wave exposure • Temp, salinity, desiccation – Effects of wave shock • What else effects organismal distribution? • Food / nutrients • Trophic interactions – – – – – Many suspension feeders Grazers Scavengers Predators Detritus is central • typically most important food source Fig. 11.15 Fig. 11.16 • Space is typically most limiting resource • Most organisms are attached to substrate – Mussel species – Barnacle species – Anemones, seaweed • Much competition for any freed-up space Fig. 11.17 What is happening here? • Juvenile sea palm settled on mussels – Increased profile and drag increases vulnerability of wave shock • Mussel clumps detach • Makes space for juvenile sea palms on substrate Fig. 11.19 Trophic interactions & environmental adaptations define zones • Vertical zonation – Patterns or banding of distribution – Upper limit set by physical factors • Space often defines upper end of range – zones • Exposure – Lower limit set by biotic factors • Predation • Competition Fig. 11.18 Fig. 11.20 Fig. 11.21 Diversity and abundance • At Scripps intertidal, organismal diversity was high. • Species abundance varies with diversity – Mussels in mod. abundance; Barnacles – mod.; Sea stars – mod. • Keystone predators – A predatory species that significantly affects the community beyond their abundance – Can maintain diversity Fig. 11.22 Fig. 11.23 Page 252 Fig. 11.23 & 11.24 Predation on dominant competitors = disturbance • ↓ predation = ↓ disturbance = competitive exclusion • ↑ disturbance = ↓ establishment = ↓ diversity • Moderate disturbance = provides a balance between abiotic and biotic factors; a chance for diverse species Fig. 11.33 & 11.34 What about sandy intertidal areas? Beaches? • Still get zonation patterns… – However, here many organisms are adapted for sand/sediments rather than rocks and tidepools