Lecture 5: Biodiversity and Conservation of the Ocean; Ecosystems Ecology, Productivity, and Trophic Structure

Biodiversity and Conservation of the Ocean

Marine Biogeography Biogeography = the study of the geographical distribution and abundance of species through out the ocean Present distribution of species is the result of speciation, dispersal, and extinction Marine biota can be divided into geographic provinces cec.org

Factors in Biodiversity Local patterns of species diversity are often controlled by short-term ecological interactions Regional patterns are probably controlled by the balance of speciation and extinction Speciation (formation of new species) usually requires some degree of isolation of populations Extinction can be caused by habitat change or destruction, widespread diseases, biological interactions, or random fluctuations of population size

ARCTIC ALEUTIAN OREGONIAN CALIFORNIAN 70N 60N 50N 40N 30N 1. Pt. Barrow 2. Cape Romanzof 3. Nunivak Island 4. Hagemeister Island 5. Prince William Sound 6. Dixon Entrance 7. Vancouver Island 8. Puget Sound 9. Cape Flattery 10. Cape Mendocino 11. Monterey Bay 12. Point Conception 13. Punta Eugenia 14. Cabo Sa n Lucas Provinces (named in red) of the Pacific coast of North America

Establishment of Biogeographic Barriers Many coastal provinces are maintained by barriers to dispersal (ex. currents), combined with temperature breaks Larger scale barriers originate from geological upheavals, resulting in isolation and speciation

Relating Geography to Evolutionary History The relation of geography to speciation can be accomplished by relating evolutionary trees to patterns of geographic occurrence

Relating Geography to Evolutionary History Importance of barriers: different groups of evolutionarily related species found on east and west side of the Pacific, resulting from long-term geographic isolation; most closely related species found on either side of Isthmus of Panama, which arose about 3 million years ago

Within-species level - trace genetic markers and fossils show: dispersal 3.5 million years ago from Pacific to Atlantic then extinction by glaciers on Atlantic side in New England-Nova Scotia 18,000 years ago then re-colonization of this area from European side of Atlantic about 4000 years ago Relating Geography to Evolutionary History

Persistent boundary can isolate populations of several species

Components of Species Diversity Alpha diversity () = Within-habitat diversity Beta diversity () = Between-habitat diversity. A contrast of diversity in two locales of differing habitat type. Gamma diversity () = Regional diversity

Concepts of Species Diversity Diversity and stability Early discussions of tropical vs. temperate; polluted vs. non- polluted areas Diversity and productivity Recent discussions about a possible relationship

Diversity Gradients Latitudinal diversity gradient - one of the most pervasive gradients; number of species increases toward the equator Gradient tends to apply to many taxonomic levels (species, genus, etc.)

Latitudinal species richness gradients Ex. land birds

Factors Hypothesized to Influence Biodiversity (& Latitudinal Gradients) FactorRationale HistoryMore time permits more complete colonization and the evolution of new species Spatial heterogeneityPhysiologically or biologically complex habitats furnish more niches Competitiona.Competition favors reduced niche breadth b.Competitive exclusion eliminates species PredationPredation hampers competitive exclusion ClimateClimatically favorable conditions permit more species Climatic variabilityStability permits specialization ProductivityRichness is limited by the partitioning of production among species DisturbanceModerate disturbance hampers competitive exclusion Source: Modified after Pianka (1988) and Currie (1991)

Recent Explanations for Latitudinal Diversity Gradients Increased area of the tropics Increased effective evolutionary time due to shorter generation times in the topics

Other Diversity Differences Between-ocean differences: Pacific biodiversity appears to be greater than Atlantic Within-ocean differences: from a central high of biodiversity in the SW Pacific, diversity declines with increasing latitude and less so with increasing longitude, away from the center Inshore-estuarine habitats: estuaries tend to be lower in diversity than open marine habitats Deep-sea diversity increases, relative to comparable shelf habitats, then decreases to abyssal depths

Explanations of Diversity Differences Area - greater area might result in origin of more species (b/c of larger diversity of habitats within a larger area), but also lower extinction rate of species living over greater geographic ranges (b/c of higher population sizes, and presence of more refuge habitats)

Effects of Area and Food Supply

Explanations of Diversity Differences Short-term ecological interactions - presence of predators might enhance coexistence of more competing species, competitor might drive inferior species to a local extinction Complex recent historical events - may explain some current regional differences in species diversity (e.g., diversity gradient in tropical American coral reefs may be partially due to extinctions around periphery of province)

Explanations of Diversity Differences Habitat stability - a stable habitat may reduce the rate of extinction, because species could persist at smaller population sizes (possible explanation of deep-sea maximum of species richness) Sea-level fluctuations - sea level fluctuations, such as during the Pleistocene, might have created barriers during low stands of sea level, leading to isolation and speciation. This mechanism has been suggested as increasing the number of species in the SW Pacific in coral reef areas

Explanations of Diversity Differences Greater speciation rate - might explain higher diversity in tropics; center of origin theory argues that tropics are source of most new species, some of which may migrate to higher latitudes Lower extinction rate - might also explain major diversity gradients

Is There a Center of Origin? Center of Origin Hypothesis: high diversity centers are places where more species are produced and retained and also a source of colonization to peripheral regions where diversity is lower

Within the Pacific Ocean, species diversity in coral reefs declines in all directions from an Indo-Pacific diversity maximum

Example of evidence supporting the center of origin theory: Number of sea grass species with distance down-current from Torres Straight

Jablonski et al.* looked at first fossil occurrences of members of a genus in the fossil record First occurrences occur much more frequently in tropics than at high latitude Conclude: Center of Origin hypothesis is supported *D. Jablonski et al., Science 314, 102 -106 (2006) Fossil Record Evidence in Support of Center of Origin Hypothesis

Research in Marine Biodiversity Understand patterns, processes, and consequences of changing diversity in the sea by focusing on the effects of human activities. Increase understanding of how larger-scale oceanographic processes may impact smaller- scale biodiversity patterns and processes. Strengthen field of marine taxonomy. Encourage new technology, development of predictive models, and look at things from historical perspectives. Improve predictions concerning human impacts on the ocean.

Conserving Marine Biodiversity In many habitats the number of species present is poorly known and severely underestimated Need methods of recognizing species; morphology has limited use, but molecular markers are being used commonly to distinguish among species

Shifting Baselines Diversity & ecosystem structure today may be strongly altered relative to a few human generations ago We might mistakenly take todays situation as the baseline for conservation The baseline for a natural community has shifted over generations because we have forgotten the original natural state

Conserving Marine Biodiversity: Value of Biodiversity Aesthetic value of diverse ecosystems Many species play crucial roles in elemental cycling Loss of species at apex of food chains has drastic top- down effects on marine systems Loss of species that are structural elements in communities (e.g., corals, seaweeds, seagrasses) might cause loss of many more species More diverse ecosystems may be more resilient, extinction of one species results in expansion of ecological function by another species

Conservation Strategies Individual species - preserve abundance of target species, such as large carnivores, marine mammals Conserve total biodiversity of a region - focus on hotspots of high diversity

Conservation Strategies Conserve ecosystem function - concern is focused on species that are important in ecosystem processes (such as primary production, nutrient cycling, decomposition) higher biodiversity might enhance some functions, such as total productivity Establish economic value of ecosystem by evaluating its ecosystem services - ecosystems have human value that can be quantified in money (resources, water supply, recreation, etc.)

Conservation Strategies Marine Protected Areas (Marine Reserves) Set aside a fraction of ecosystem area/volume to allow populations to thrive and spill over into remaining unprotected sites Population density, body size, biomass, biodiversity all found to be higher within marine reserves

Marine Invasions Threat to Biodiversity Invasion = the arrival of a species to an area that has not lived there previously Increasing in frequency Often result in the arrival of species with strong local ecological effects Eventually homogenize the biota world-wide

Properties of Successful Invaders Vector - a means of transport must be available, e.g., ballast water of ships, ability to disperse (e.g., planktotrophic larvae) Invasion frequency - because most arrivals do not result in invasion success, frequency of arrival is important Ecological suitability of target habitat - invading species need an appropriate habitat in which to colonize and propagate Survival of initial population variation - initial fluctuations of small population size results in extinction of invading species

Methods of Invasion Ship ballast water Transport of commercially exploited mariculture species Canals Biological control Aquarium/Pet industry

Invaders Can Have Significant Effects Periwinkle Littorina littorea Shore crab Carcinus maenas Freshwater zebra mussel, Dreissena polymorpha

Invasion routes of species of the crab genus Carcinus maenas from European waters to sites around the world

Ecosystems Ecology, Productivity, and Trophic Structure

Ecosystem Level Ecosystem = An entire habitat, including all abiotic features of the landscape/seascape and all the living species within it that interact Focus is on: Energy flux Biological productivity Nutrient cycling

Ecological Processes Ecosystem Level Primary producers (autotrophs) organisms that produce organic molecules. Primarily photosynthetic Primary consumers (herbivores) consume autotrophs Secondary consumers (carnivores) consume herbivores Tertiary productivity

Productivity vs. Biomass Biomass is the mass of living material present at any time, expressed as grams per unit area or volume Productivity is the rate of production of living material per unit time per unit area or volume

Productivity Primary productivity - productivity due to photosynthesis Secondary productivity - productivity by the consumers of primary producers

Productivity by Ecosystems per m 2

Productivity by Ecosystems Global Basis

Measuring Primary Productivity Gross primary productivity - total carbon fixed during photosynthesis Net primary productivity - total carbon fixed during photosynthesis minus that part which is respired Most interesting gives that part of the production available to higher trophic levels

Measuring Primary Productivity Remote Sensing Satellite color scanners can give an estimate of photosynthetic pigment concentration Relationship between chlorophyll concentration and primary production varies with region Need ground-truthing to determine relationship

Measuring Primary Productivity Remote Sensing

Satellite image of estimated chlorophyll in water column, from SeaWiFS satellite (Sea-viewing Wide Field-of-view Sensor) Measuring Primary Productivity Remote Sensing Coccolithophore bloom from space - satellite photograph

Geographic Variation of Productivity Continental shelf and open-ocean upwelling areas are most productive Coastal areas are nutrient-rich and productive Convergences and fronts often are sites of rise of nutrient rich deep waters Central ocean, gyre centers are nutrient poor, low primary production

Geographic Variation of Productivity

Why are ocean waters more productive in the higher latitudes than in the lower latitudes? In higher latitudes, have seasonal mixing (in winter) that occurs when thermocline breaks down towards the end of fall. In lower latitudes, surface water temps remain somewhat constant. Do not have seasonal breakdown of thermocline.

Food Chains and Food Webs Trophic level a species or group of species that feed on one or more other species (which can be grouped into a lower trophic level) Food chain - linear sequence showing which organisms consume which other organisms, making a series of trophic levels Food web - more complex diagram showing feeding relationships among organisms, not restricted to a linear hierarchy

Trophic Levels Defines how far an organism is removed from the producer in obtaining its nourishment Producers-always trophic level 1 Herbivores-always trophic level 2 Higher order consumers may occupy different trophic levels depending on what they are feeding on at any point in time

Trophic Levels Primary Producers Phytoplankton and macrophytes Consumers: heterotrophic animals Primary consumers: herbivores Secondary and higher-level consumers: carnivores, predators Decomposers: bacteria and fungi Trophic level Name 4 Top carnivore 3 Carnivore 2 Herbivore 1 Autotroph

Food Chains The energy flow from one trophic level to the other is known as a food chain It involves one organism at each trophic level Primary Consumers eat autotrophs (producers) Secondary Consumers eat the primary consumers Tertiary Consumers eat the secondary consumers Decomposers bacteria and fungi that break down dead organisms and recycle the material back into the environment

Simplified food chain taken from a food web

Food Chains The total number of links in a food chain may be limited by: 1. the structure of the food chain 2. the possible energy that can be transported through many links 3. possible instability of large food chains Unusual to find more than 4-5 trophic levels in food chains

Food Chains - Structure Bottom up control: control of food chain by amount of primary production Top-down control: control of food chain by variation in top predators Three-level food chains: Primary producers will be abundant because the herbivore population is reduced by the carnivores Remove top level (carnivore) and herbivore increases, resulting in low population size of primary producer. Even-numbered food chains: Primary producers tend to be rare

Food Chains - Energy Transfer Trophic Hypothesis there is a maximum number of trophic links through which energy can travel With ecological efficiency of 10%, only 0.01% will reach a 5 th trophic level May set a limit to upper trophic levels bottom- up control

Food Chains - Stability Food Chain Stability Hypothesis Longer food chains are inherently unstable Changes at one level will propagate to other levels If a population at one trophic level goes extinct, it will cause species at levels above it to go extinct Omnivory feeding on many food sources (i.e. different trophic levels) Reduces effects of fluctuations of a species in a given level of a food chain

Food Webs Community food web is a description of feeding habits of a set of organisms based on taxonomy, location or other criteria Rule: The more intricate the food web the more stable the ecosystem

Food Webs Food webs portray flows of matter and energy within the community If community is like a city, then Food Web is like a street map of a city Web omits some information about community properties e.g., minor energy flows, constraints on predation, population dynamics

Descriptive Food Webs

Interaction or functional food webs depict the most influential link or dynamic in the community

Food Webs: Methods of Study 1.Identify component species 2.Sample to determine who is eating whom 3.Sampling and gut analysis to quantify frequency of encounters 4.Exclosures and removals of species to determine net effects 5.Stable isotopes 6.Mathematical models

Food Web Analysis Modern Approaches to Food Web Analysis Connectivity relationships Importance of predators and interaction strength in altering community composition and dynamics Identification of trophic pathways via isotope analysis. Weakness of above: no quantitative measure of food web linkages.

Food Webs: Complexity meets Reality Fallacy of linear food chains as a adequate description of natural food webs Food webs are reticulate Discrete homogeneous trophic levels an abstraction or an idealism omnivory is rampant ontogenetic diet shifts (sometimes called life history omnivory) environmental diet shifts spatial & temporal heterogeneity in diet

Energy Flow Through Ecosystems Energy transfer between trophic levels is not 100% efficient, and energy is lost as it passes up a food chain. Herbivores eat a small proportion of total plant biomass They use a small proportion of plant material consumed for their growth. The rest is lost in feces or respiration Less energy is available at the next trophic level.

Trophic Basis of Production Assimilation efficiency varies with resource 10% for vascular plant detritus 30% for diatoms and filamentous algae 50% for fungi 70% for animals 50% for microbes (bacteria and protozoans) 27% for amorphous detritus Net Production Efficiency production/assimilation ~ 40%

Food Webs & Efficiency Ecological efficiency is defined as the energy supply available to trophic level N + 1, divided by the energy consumed by trophic level N. You might think of it as the efficiency of copepods at converting plants into fish food. In general, only about 10% of the energy consumed by one level is available to the next. Difficult to measure so food web scientists focus on measures of transfer efficiency for selected groups of animals.

Food Web Transfer Efficiency E t = P t / P t-1 Where: P t = The annual production at trophic level t P t-1 = The annual production at the lower trophic level

Transfer Between Trophic Levels Budget for ingested food (use energy units): I = E + R + G I amount ingested E amount egested R amount respired G growth (partitioned between somatic growth and reproduction) **usually constructed in terms of energy units (e.g. calories)

Transfer Between Trophic Levels Use food chain efficiency to calculate Potential production at highest trophic level: P = BE n B = primary production P = production at highest level E = food chain efficiency n = number of links between trophic levels

Food Webs and Energy Pyramid of biomass represents the amount of energy, fixed in biomass, at different trophic levels for a given point in time

Food Webs in the Ocean Pyramid of biomass for the oceans can appear inverted Pyramid of energy shows rates of production rather than biomass.

Marine Food Webs Food webs in the oceans vary systematically in food chain efficiency, number of trophic levels, and primary production Oceanic system Coastal/Shelf system Upwelling

Marine Food Webs Food Chain Type Primary Productivity gCm -2 y -1 Trophic Levels Food Chain Efficiency Potential Fish Production mgCm -2 y -1 Oceanic505100.5 Coastal/Shelf100315340 Upwelling3001.22036,000 After Ryther, 1969 Science 166: 72-76.

Variation in Planktonic Food Webs Oceanic Coastal/Shelf Upwelling

Marine Food Webs Great potential of upwelling areas due to combination of: High primary production (have high and continuous nutrient supply) Higher food chain efficiency (related to ease of ingestion and assimilation of large diatoms by planktivorous fish) Lower number of trophic levels (less overall loss of energy)

Are trophic levels useful? Even if organisms are not strict herbivores, primary carnivores, etc., as long as they are mostly feeding at one trophic level, the concept can have value (e.g., trophic cascade concept).

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Lecture 5: Biodiversity and Conservation of the Ocean; Ecosystems Ecology, Productivity, and Trophic Structure