Week 2 - Benthic Assemblages

Question 1

What did early investigators recognize about species distributions?

Answer 1

Similar species tend to be found in similar places and distributions can be distinguished across space and time.

Question 2

In what period was the discipline of classifying species formalized?

Answer 2

Late 1800s.

Question 3

Who was Aristotle and what was his contribution to natural history?

Answer 3

A student of Plato who emphasized observation as the foundation of knowledge and studied species’ habitat requirements.

Question 4

What did early marine explorers recognize about species?

Answer 4

Certain species occur in particular environmental zones.

Question 5

What was the significance of the 18th and 19th centuries in marine research?

Answer 5

Surge in species collection from undiscovered regions.

Question 6

Who studied polychaete distributions in the 1920s?

Answer 6

Fauvel.

Question 7

What did Pruvot and Southern formalize in their research?

Answer 7

Early classifications of zoogeographic zones.

Question 8

What did Pruvot (1897) recognize about the seabed?

Answer 8

Seemingly homogeneous patches of seafloor contained subtle differences.

Question 9

What is the concept of facies introduced by Pruvot?

Answer 9

Zones distinguished by sediment type and associated fauna.

Question 10

What are the two types of fauna differentiated by Southern (1915)?

Answer 10

• Microlithic fauna (infauna) * Macrolithic fauna (epifauna)

Question 11

What is biocoenosis as introduced by Mobius (1877)?

Answer 11

Recognizing interactions between fauna and the sediment biotope.

Question 12

What did Mobius (1877) lack in his introduction of biocoenosis?

Answer 12

Practical applications.

Question 13

What did Petersen (1914-1924) contribute to assemblage research?

Answer 13

Emphasized quantitative sampling and developed the Petersen grab.

Question 14

What did Molander (1928) define as animal communities?

Answer 14

Recurring combinations of species, often abundant numerically.

Question 15

What definition of an assemblage was provided by Mills (1969)?

Answer 15

A group of organisms occurring in a particular environment, interacting with each other and separable by ecological survey.

Question 16

What shift occurred in assemblage research methodologies?

Answer 16

From qualitative to quantitative sampling methodologies.

Question 17

What is the difference between community and assemblage?

Answer 17

• Community: Full interacting group of species * Assemblage: Subset, particularly macrofaunal invertebrates

Question 18

What unique challenges does the benthic environment present?

Answer 18

Spatial heterogeneity and environmental gradients.

Question 19

What challenge is associated with determining assemblage consistency?

Answer 19

Whether assemblages are uniform over vast sea floor regions.

Question 20

What analogy did Petersen (1914-1924) use to describe the challenges of dredging surveys?

Answer 20

Comparing a dredging ship to an airship towing a net over a city.

Question 21

What was the primary focus of Petersen’s Kattegat Study?

Answer 21

Comprehensive benthic survey in shallow waters

Conducted from 1914 to 1924

Question 22

How many stations were sampled in Petersen’s Kattegat Study?

Answer 22

193 stations

Data collected over multiple years: 1914, 1915, 1918, and 1924

Question 23

What was the total number of faunal records collected in Petersen’s Kattegat Study?

Answer 23

294 faunal records

Collected across multiple years

Question 24

What did Petersen identify in his findings regarding benthic communities?

Answer 24

Distinct communities based on dominant species

Assemblages categorized by species constancy and dominance

Question 25

What type of classification did Petersen develop for the North Sea?

Answer 25

Species-based classification ## Footnote Communities distinguished by characteristic species

Question 26

How many major benthic communities did Petersen identify?

Answer 26

7 major benthic communities

Question 27

Who was Johannes Petersen?

Answer 27

Danish marine biologist (1860–1928) focused on fisheries and benthic invertebrate fauna

Question 28

What limitations did Petersen recognize in traditional sampling methods?

Answer 28

Limitations of qualitative sampling methods (e.g., dredges) ## Footnote Emphasized need for quantitative approaches

Question 29

What innovative sampling approach did Petersen develop?

Answer 29

Quantitative sampling using the Petersen grab

Question 30

What is the Characterising Species Concept in benthic ecology?

Answer 30

Assemblages can be described by dominant species ## Footnote Constancy and dominance determine community definition

Question 31

List the names of the 7 major benthic communities identified by Petersen.

Answer 31

* Macoma balthica community (bivalve) * Brissopsis community (urchin, Brissopsis lyrifera) * Echinocardium community (urchin, Echinocardium cordatum) * Astarte-Macoma-Abra community (bivalves) * Venus community (bivalve, Venus striatula) * Macoma calcarea community (bivalve) * Haploops community (amphipod, Haploops tubicola) ## Footnote Each community named after a dominant species

Question 32

What did Petersen’s community classification aim to achieve?

Answer 32

Simplified complex datasets into recognizable types

Question 33

What was the main argument of Jones regarding environmental factors?

Answer 33

Physical factors drive species distributions ## Footnote Factors include temperature, salinity, and sediment type

Question 34

What zoogeographical regions did Jones propose?

Answer 34

* Arctic (-2 to 7°C) → 4 associations * Atlantic Boreal (3 to 16°C) → 3-tiered structure ## Footnote Arctic includes shallow water, offshore sand, muddy-sand, deep mud

Question 35

What did Thorson (1957) refine in species classification?

Answer 35

Introduced ideal rules to define dominant & subdominant species quantitatively ## Footnote Built on Petersen and Jones’ work

Question 36

How many global community types did Thorson recognize?

Answer 36

7 global community types based on habitat & depth ## Footnote Examples include Macoma, Venus, Abra

Question 37

What is the Parallel Communities Concept?

Answer 37

Communities with similar structures but different species exist globally ## Footnote Example: Macoma, Cardium, Mya communities in different locations

Question 38

What mixed evidence exists regarding Petersen-Jones-Thorson communities in warm waters?

Answer 38

Some studies supported parallel communities; others did not ## Footnote Examples include West Africa and California vs. Gulf of Mexico and Thailand

Question 39

What did Stephenson et al. (1972) find in their reanalysis of Petersen’s data?

Answer 39

Presence/absence data largely aligned with Petersen’s original communities; abundance & biomass data produced different groupings ## Footnote Petersen’s bias toward ubiquitous species affected results

Question 40

What are the four main assemblages described by Jones (1950)?

Answer 40

* Shallow water (Macoma) * Offshore sand (Venus) * Offshore muddy-sand (Astarte) * Deep mud (Foraminifera) ## Footnote Introduced zoogeographical regions to refine Petersen’s classification

Question 41

What is the three-tiered hierarchical system developed by Jones?

Answer 41

* A. Shallow water & brackish communities * B. Offshore communities * C. Deep-sea communities ## Footnote Further divided by substrate type and sediment type

Question 42

What was the key finding of the case study conducted in Galway Bay?

Answer 42

42,934 individuals from 147 taxa identified ## Footnote 78.5% classified to species level

Question 43

What were the individual counts and biomass results from the Leverets Site in Galway Bay?

Answer 43

* 7,832 individuals * 144.48g biomass * 91 taxa ## Footnote Conducted by O’Connor et al. (1993)

Question 44

What environmental variables were measured in the water column data?

Answer 44

* Oxygen (O₂) * Nutrients (NH₄, NOₓ, PO₄, SiO₂) * Suspended Particulate Matter (SPM) * Particulate Organic Carbon (POC) ## Footnote Using a 5L Van Dorn water bottle

Question 45

What sediment data metrics were collected using a 55mm Craib corer?

Answer 45

* Organic Carbon (OrgC) * Porosity and mean particle size (d50) * Grain size distribution metrics (Mz, IGSD, IGS) * Laser-based particle size analysis (d32, d43) ## Footnote Important for assessing sediment characteristics