Marine Biodiversity Notes

Biodiversity Defined

  • Bio = life

  • Diversity = variety

  • Biodiversity = variety of life

  • 3 types of diversity:

    1. Genetic

      • Variation w/in a spp

    2. Species

      • Types of organisms

    3. Ecosystem

      • Different types of habitats, biotic communities, or ecological processes

Introduction

  • Bio = life

  • Diversity = variety

  • Biodiversity = variety of life

  • 3 types of diversity:

    1. Genetic

      • Variation w/in a spp

    2. Species

      • Types of organisms

    3. Ecosystem

      • Different types of habitats, biotic communities, or ecological processes

  • Measuring Biodiversity:

    • Spp richness

      • Number of different spp in a particular habitat

      • Presence / absence

    • Spp abundance (evenness)

      • Relative number of each type of spp in a particular habitat

      • Quantification of those spp present

Whittaker's alpha, beta and gamma diversities

  • Alpha diversity is local diversity or species diversity at a site.

    • Estimated by species richness or by one of the alpha diversity indices (richness, Shannon, Simpson).

  • Beta diversity is spatial differentiation - or the variation in species composition among sites within a region of interest.

    • B=Y/aB = Y/a

  • Gamma diversity is regional diversity - or species diversity in a region of interest.

    • Estimated by pooling observations from a large number of sites in the area and computing an alpha diversity index.

  • Robert Whittaker (1960, 1972).

Spatial Scales of Diversity

  • Gamma Diversity = number of species observed in all habitats within a region (i.e., regional diversity)

  • Robert Whittaker

  • Beta Diversity among-habitat diversity

    • Rate of species turnover between habitats

    • Expressed as Gamma/Alpha diversity

  • Alpha Diversity = local diversity within a uniform habitat type (i.e., within-habitat diversity)

  • alpha-diversity (a) = diversity intra

  • beta-diversity (B) = diversity inter

  • gamma-diversity (y)= total diversity

  • B=(−a)/yB = (-a)/y

N distinct compositional units (3 different communities)

  • When local (α) = regional (ϒ) spp richness, their ratio (Β) equals unity (1).

  • Β = ϒ/α

  • Sites = white circles

  • Regions = blue rectangles

Linnaeus

  • Connections between classes

  • Reflect back to MAR250

    • Prokaryota

    • Monera

    • Protista

    • Eukaryota

    • Fungi

    • Animalia

    • Plantae

The comparative richness of marine habitats in terms of animal phyla

  • Often biodiversity is calculated based on genus or phyla, instead of spp.

  • Why?

Marine species richness in geological time

  • Changes in diversity can be observed over short timescales (10,000 yrs) or long geologic timescales (100,000,000 yrs).

  • Marine biodiversity generally INCREASES or DECREASES after a mass extinction? (Sala & Knowlton 2006; Benton & Emerson 2007)

  • Permian/Triassic : 90% of all marine spp may have gone extinct

  • Now, at least twice as many marine invertebrates than 200mya (Figure 2.5)

  • Threat to biodiversity

    • Global Climate Change (Temperature) Anthropocene

Differences in the distribution of biomass and species number

  • Spp number hotspots do not necessarily correspond to spp biomass hotspots

  • Total number of epibenthic species in the North Sea in 2000.

    • (a)Total number of epibenthic species. (b) Mean epibenthic biomass. Numbers are based on wet-weight of free living species.

    • Callaway et al. 2002. Diversity and community structure of epibenthic invertebrates in the North Sea. ICES Journal of Marine Science. 59:1199-1214

  • Biodiversity

  • Biomass

Present marine species richness

  • COML

    • Census of Marine Life

    • http://www.coml.org/

  • OBIS

    • Ocean Biogeographic Information System

    • https://obis.org/

  • WoRMS

    • World Register of Marine Species

    • http://www.marinespecies.org/

We know more about some areas than others

  • We know something about:

    • Nearshore

    • Oceans surrounding developed nations

  • We know very little about:

    • Hydrothermal vent

    • Deep ocean

    • Arctic and Antarctic

    • Oceans surrounding developing nations

Factors that correlate with biodiversity and species richness (BIG 10)

  1. sample size and sampling effort

  2. body size

  3. depth

  4. latitude and longitude

  5. habitat size

  6. habitat complexity

  7. disturbance

  8. productivity

  9. grazing and predation

  10. genetics and dispersal

1. Sample size and sampling effort

2. Body Size

  • Within a habitat, Is there a greater number of LARGE or SMALL individuals?

  • Sampling and sorting methods are size selective.

  • Difficult to compare spp richness between samples collected using different methods

Body Size

  • Body size drivers hypotheses.

3. Depth

  • There are fewer species in the deep sea than continental shelves due to the lower temperature, productivity, and habitat heterogeneity in the deep sea.

  • R2=0.97R^2 = 0.97

3. Depth

  • Rappaport’s Rule (with depth)

    • “High presence of short-ranged species on the continental shelf area; while only a few species reach abyssal depths, and they tend to show extremely wide bathymetric ranges.”

3. Depth

  • Rappaport's Rule (with depth)

  • y=14150x−1.75y= 14150x^{-1.75}

  • R2=0.921R^2 = 0.921

4. Latitude and longitude: Geographical variation in marine diversity

  • Units = species richness

  • A – gastropods molluscs, B – decapod crustaceans, C – polychaetes, D – bivalves molluscs, E – corals

  • Latitudinal and Longitudinal Patterns of taxon richness

    • Highest diversity in tropics COML

    • Higher diversity correlated with warmer waters

    • Coastal spp show maximum diversity in Western Pacific

    • Ocean-dwelling species peak in mid-latitudes

4. Latitude and longitude

  • Longitude: Greater species richness on WESTERN or EASTERN side of the ocean?

  • Latitude: Greater species richness at POLES or EQUATOR?

  • Exceptions:

    • Shark, tuna, swordfish have hotspots between 20∘-30∘ North & South, which are good hunting grounds for them.

    • Pycnogonids are diverse in Antarctic waters.

    • Brachiopods are not found north of equator in Pacific, and have typical latitudinal gradient in Atlantic.

4. Latitude and longitude

  • Why are there more species in the tropics?

    • This is still debated in literature

    • Different reasons for different types of organisms

    • A few compelling hypotheses:

      1. Longer evolutionary history

      2. Higher productivity (can support more species)

      3. Shorter generation times and faster rates of evolution

5. Habitat Size

  • Large habitats will support a HIGHER or LOWER number of species?

  • More habitat (volume/ area covered) = more species

  • Primarily through INCREASED COLONIZATION or DECREASED EXTINCTION?

  • note: depth or latitude ranges are not considered habitats

  • many habitat locations or sizes might be present w/in a single depth range or latitude range  See lecture slides on Island Biogeography

6. Habitat complexity

  • Large areas of homogeneous habitat are unlikely to support large numbers of species

7. Disturbance

  • The greatest biodiversity is found in areas of HIGH or INTERMEDIATE or LOW disturbance?

  • Intermediate Disturbance Hypothesis – see lecture slides on Disturbance

8. Productivity

  • When nutrient levels become high (higher productivity of waters), species diversity is HIGH or LOW?

  • It depends

    • Coral reefs become less diverse in water with high nutrient concentrations (D’Angelo & Wiedenmann 2014)

    • Connection to lecture on phase shifts

    • Bivalve molluscs, which filter-feed plankton, are more species rich (& have higher growth rates) in nutrient-enriched (eutrophic) waters

8. Productivity

  • Nutrients impact Trophic Cascades

9. Grazing and predation

  • How do higher trophic levels influence species diversity of lower trophic levels?

    • Top-down forcing

    • Trophic cascades

    • Keystone predators

    • Regime shifts/ phase shifts

10. Genetics and dispersal

  • Spatial genetic variability is linked to geographic distances between populations and the ability of species to disperse.

  • Concern: human activities have reduced genetic variability of many populations, resulting in reduced ability to respond to future environmental challenges.

Conclusions

  • Why is biodiversity important?

    1. Genetic

    2. Species

    3. Ecosystem

  • What are some threats to biodiversity?

To guide your thinking through the BIG 10

  • You will have more species in a habitat when…

    • The environment is productive and has favorable conditions to support life

    • Increase in colonization

    • Decrease in extinction

    • A dominant competitor is suppressed