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

2. Biodiversity and Conservation of the Ocean

3. 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

4. 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

5. Provinces (named in red) of the Pacific coast of North America
ARCTIC
70N
ALEUTIAN
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 San Lucas
60N
50N
OREGONIAN
40N
CALIFORNIAN
30N
Provinces (named in red) of the Pacific coast of North America

6. 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

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

8. 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

9. Relating Geography to Evolutionary History
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

10. Persistent boundary can isolate populations of several species

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

12. 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

13. 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.)

14. Latitudinal species richness gradients
Ex. land birds

16. Factors Hypothesized to Influence Biodiversity (& Latitudinal Gradients)
Rationale
History
More time permits more complete colonization and the evolution of new species
Spatial heterogeneity
Physiologically or biologically complex habitats furnish more niches
Competition
Competition favors reduced niche breadth
Competitive exclusion eliminates species
Predation
Predation hampers competitive exclusion
Climate
Climatically favorable conditions permit more species
Climatic variability
Stability permits specialization
Productivity
Richness is limited by the partitioning of production among species
Disturbance
Moderate disturbance hampers competitive exclusion
Source: Modified after Pianka (1988) and Currie (1991)

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

18. 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

19. 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)

21. Effects of Area and Food Supply

22. 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)

23. 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

24. 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

25. 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

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

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

28. Fossil Record Evidence in Support of Center of Origin Hypothesis
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, (2006)

29. 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.

30. 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

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

32. 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

33. 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

34. 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.)

35. 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

36. 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

37. 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

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

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

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

41. Ecosystems Ecology, Productivity, and Trophic Structure

42. 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

43. 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

44. 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

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

46. Productivity by Ecosystems – per m2

47. Productivity by Ecosystems – Global Basis

48. 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

49. 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

50. Measuring Primary Productivity – Remote Sensing

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

52. 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

53. Geographic Variation of Productivity

54. 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.

55. 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

56. 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

57. Trophic Levels 4 Top carnivore 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

58. 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

59. Simplified food chain taken from a food web

60. 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

61. 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

62. 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 5th trophic level
May set a limit to upper trophic levels → bottom-up control

63. 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

64. 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

65. 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

66. Descriptive Food Webs

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

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

69. 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.

70. 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

71. 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.

72. 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%

73. 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.

74. Food Web Transfer Efficiency
Et = Pt/ Pt-1
Where:
Pt = The annual production at trophic level t
Pt-1 = The annual production at the lower trophic level

75. 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)

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

77. 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

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

79. 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

80. Marine Food Webs Food Chain Type Primary Productivity gCm-2y-1
Trophic Levels
Food Chain Efficiency
Potential
Fish Production
mgCm-2y-1
Oceanic 50 5 10
0.5
Coastal/Shelf
100 3 15
340
Upwelling
300
1.2 20
36,000
After Ryther, 1969 Science 166:

81. Variation in Planktonic Food Webs
Oceanic
Coastal/Shelf
Upwelling

82. 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)

83. 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).