Substrate and Time of Day Effects on Benthic Organisms

Trawling Meet at RV EO Wilson at 2:00 pm Meet at RV EO Wilson at 2:00 pm If not on meal plan, bring your own food If not on meal plan, bring your own food Will return to dock around 10:00pm Will return to dock around 10:00pm Take your motion sickness medicine minutes BEFORE you get on boat Take your motion sickness medicine minutes BEFORE you get on boat

Bottom Trawling in Action Effective sampling method Effective sampling method Commercial trawling is responsible for major depletion of continental shelves, enormous bycatch, and habitat destruction Commercial trawling is responsible for major depletion of continental shelves, enormous bycatch, and habitat destruction Likened to clear cutting of forests (Watling and Norse 1999) Likened to clear cutting of forests (Watling and Norse 1999)

Similarity Calculations Compare similarity in fish/invert species composition during day between: Compare similarity in fish/invert species composition during day between: Mud-Sand; Mud-Shell; Sand-Shell (Day and Night) Mud-Sand; Mud-Shell; Sand-Shell (Day and Night) Use Jaccard similarity index: Use Jaccard similarity index: J = C / (A+B-C) J = C / (A+B-C) A = No. of spp. on substrate 1 A = No. of spp. on substrate 1 B = No. of spp. On substrate 2 B = No. of spp. On substrate 2 C = No. of spp. shared by both substrates C = No. of spp. shared by both substrates Value varies from 0 (no common spp.) to 1 (all common) Value varies from 0 (no common spp.) to 1 (all common)

Similarity Calculations MudSandShell Mud1 Sand1 Shell1 If Sand has 22 spp. Mud has 20 spp. 10 spp. overlap J = 10 / ( ) J =

Euclidean Distance Considers the distribution of individuals with species in each collection: Considers the distribution of individuals with species in each collection: Delta JK = Sqrt [ Sum (X ij – X ik ) 2 ] Delta JK = Sqrt [ Sum (X ij – X ik ) 2 ] Delta JK = Euclidean Distance Delta JK = Euclidean Distance X ij = Number indiv’s of species “i” in collection “j” X ij = Number indiv’s of species “i” in collection “j” X ik = Number indiv’s of species “i” in collection “k” X ik = Number indiv’s of species “i” in collection “k” n = Total number of species n = Total number of species

Euclidean Distance Compensate for fact that Euclidean Distance increases with number of species in a sample by calculating average distance: Compensate for fact that Euclidean Distance increases with number of species in a sample by calculating average distance: d jk = [ Sqrt ( Delta 2 jk ) ] / (n) d jk = [ Sqrt ( Delta 2 jk ) ] / (n) d jk = average Euclidean distance b/n sample j and k d jk = average Euclidean distance b/n sample j and k Delta jk = Euclidean Distance Delta jk = Euclidean Distance n = number of species in the samples being compared n = number of species in the samples being compared

Euclidean Dist. Calculations Site 1Site 2Site 3 Sp Sp Sp ED 1,2 = sqrt [ ( ) 2 + (20-10) 2 + (0-5) 2 ] ED 1,3 = sqrt [ ( ) 2 + (20-5) 2 + (0-0) 2 ] ED 2,3 = sqrt [ ( ) 2 + (10-5) 2 + (5-0) 2 ]

Questions Explain why you found the similarity values you did, using material from lecture, notes, text, observations Explain why you found the similarity values you did, using material from lecture, notes, text, observations Discuss why Jaccard and Euclidean distances showed different patterns (if they did) Discuss why Jaccard and Euclidean distances showed different patterns (if they did) Describe similarities and differences in body shape, shell thickness, and general morphology of the taxa inhabiting various structures Describe similarities and differences in body shape, shell thickness, and general morphology of the taxa inhabiting various structures