Bryozoans as palaeoenvironmental indicators Paul D Taylor, NHM, London Friday, 7 October 2011 What are bryozoans? Friday, 7 October 2011 What are bryozoans? • invertebrate phylum Friday, 7 October 2011 What are bryozoans? • invertebrate phylum • >6000 living species Friday, 7 October 2011 What are bryozoans? • invertebrate phylum • >6000 living species • mainly marine Friday, 7 October 2011 What are bryozoans? • invertebrate phylum • >6000 living species • mainly marine • intertidal to 8000 m depth Friday, 7 October 2011 What are bryozoans? • invertebrate phylum • >6000 living species • mainly marine • intertidal to 8000 m depth • suspension feeders Friday, 7 October 2011 What are bryozoans? • invertebrate phylum • >6000 living species • mainly marine • intertidal to 8000 m depth • suspension feeders • all colonial Friday, 7 October 2011 What are bryozoans? • invertebrate phylum • >6000 living species • mainly marine • intertidal to 8000 m depth • suspension feeders • all colonial • usually sessile, benthic Friday, 7 October 2011 What are bryozoans? • invertebrate phylum • >6000 living species • mainly marine • intertidal to 8000 m depth • suspension feeders • all colonial • usually sessile, benthic • most have CaCO3 skeletons Friday, 7 October 2011 What are bryozoans? • invertebrate phylum • >6000 living species • mainly marine • intertidal to 8000 m depth • suspension feeders • all colonial • usually sessile, benthic • most have CaCO3 skeletons • Ordovician-Recent Friday, 7 October 2011 Bryozoan colony-forms Friday, 7 October 2011 Robert Hooke’s illustration of Flustra from Micrographia (1665) Friday, 7 October 2011 Friday, 7 October 2011 Friday, 7 October 2011 125 Phanerozoic bryozoan family diversity 100 75 families 50 cheilostomes 25 0 500 400 300 200 100 0 Ma ORDOVICIAN PRESENT DAY Friday, 7 October 2011 125 Phanerozoic bryozoan family diversity 100 Ordovician radiation 75 families 50 cheilostomes 25 0 500 400 300 200 100 0 Ma ORDOVICIAN PRESENT DAY Friday, 7 October 2011 125 Phanerozoic bryozoan family diversity 100 Ordovician radiation Permian extinction 75 families 50 cheilostomes 25 0 500 400 300 200 100 0 Ma ORDOVICIAN PRESENT DAY Friday, 7 October 2011 125 Phanerozoic bryozoan family diversity 100 Ordovician radiation Permian extinction 75 Cretaceous families radiation 50 cheilostomes 25 0 500 400 300 200 100 0 Ma ORDOVICIAN PRESENT DAY Friday, 7 October 2011 Abundant Upper Ordovician Cincinnati, USA rock-forming Friday, 7 October 2011 Abundant Diverse Upper Ordovician Upper Cretaceous Cincinnati, USA Maastricht, Netherlands rock-forming > 600 bryozoan species Friday, 7 October 2011 Bryozoans as palaeoenvironmental indicators 1. modern environments with bryozoans 2. colony-form analysis 3. branch diameter as a depth indicator 4. zooid size as a temperature indicator 5. palaeolatitudinal distribution of bryozoan carbonates through time [skeletal geochemistry] Akkeshi Bay Japan Friday, 7 October 2011 1. modern environments with bryozoans Friday, 7 October 2011 Modern environments colonized by bryozoans Friday, 7 October 2011 Modern environments colonized by bryozoans Freshwater bryozoans Low diversity Unmineralized Friday, 7 October 2011 Modern environments colonized by bryozoans Freshwater bryozoans Brackish bryozoans Low diversity Low diversity Unmineralized Weakly mineralized Friday, 7 October 2011 Modern environments colonized by bryozoans Freshwater bryozoans Brackish bryozoans Low diversity Low diversity Unmineralized Weakly mineralized Deep sea bryozoans Moderate diversity Weakly mineralized Friday, 7 October 2011 Modern environments colonized by bryozoans Freshwater bryozoans Brackish bryozoans Low diversity Low diversity Unmineralized Weakly mineralized Shelf bryozoans Deep sea bryozoans High diversity Moderate diversity Most species well-mineralized Weakly mineralized Friday, 7 October 2011 Recent bryozoan species diversity increasing with depth English Channel (Grant & Hayward 1985) Friday, 7 October 2011 Bryozoan assemblage species richness vs depth in the eastern (black dots) and western (white dots) North Atlantic 10 m 75 m Clarke & Lidgard 2000. Journal of Animal Ecology 69: 799-814 Friday, 7 October 2011 2. colony-form analysis Friday, 7 October 2011 Encrusng: Porella Friday, 7 October 2011 Dome shaped: 'Dianulites' Encrusng: Porella Friday, 7 October 2011 Dome shaped: 'Dianulites' Encrusng: Porella Narrow branched: Arcanopora Friday, 7 October 2011 Dome shaped: 'Dianulites' Encrusng: Porella Robust branched: Heteropora Narrow branched: Arcanopora Friday, 7 October 2011 Dome shaped: 'Dianulites' Encrusng: Porella Palmate: Phaenopora Robust branched: Heteropora Narrow branched: Arcanopora Friday, 7 October 2011 Dome shaped: 'Dianulites' Encrusng: Porella Foliose: Pentapora Palmate: Phaenopora Robust branched: Heteropora Narrow branched: Arcanopora Friday, 7 October 2011 Dome shaped: 'Dianulites' Encrusng: Porella Foliose: Pentapora Fenestrate: Chasmatopora Palmate: Phaenopora Robust branched: Heteropora Narrow branched: Arcanopora Friday, 7 October 2011 Dome shaped: 'Dianulites' Encrusng: Porella Foliose: Pentapora Fenestrate: Chasmatopora Arculated: Cellaria Palmate: Phaenopora Robust branched: Heteropora Narrow branched: Arcanopora Friday, 7 October 2011 Dome shaped: 'Dianulites' Encrusng: Porella Foliose: Pentapora Fenestrate: Chasmatopora Arculated: Cellaria Free-living: Cupuladria Palmate: Phaenopora Robust branched: Heteropora Narrow branched: Arcanopora Friday, 7 October 2011 Cheilostome bryozoan colony-forms (from Moissette 2000) can these colony-forms be used as environmental indicators? Friday, 7 October 2011 Cheilostome bryozoan colony-forms (from Moissette 2000) deep water strong currents shallow water high sedimentation can these colony-forms be used as environmental indicators? Friday, 7 October 2011 Sea-bed topography around New Zealand Otago Shelf Friday, 7 October 2011 bryozoan meadow, 100 metres Otago Shelf, New Zealand sediment from bryozoan meadow Friday, 7 October 2011 Different colony-forms represent alternative functional adaptive strategies Encrusng colonies Multiserial sheet Uniserial runner Friday, 7 October 2011 37 zooid encrusting colonies on substrates divided into equal-sized squares sheet runner Friday, 7 October 2011 37 zooid encrusting colonies on substrates divided into equal-sized squares sheet runner Runner ‘samples’ more squares of substrate and spreads a greater distance from origin (fugitive strategy) Friday, 7 October 2011 37 zooid encrusting colonies on substrates divided into equal-sized squares sheet runner Runner ‘samples’ more Sheet is compact and better squares of substrate and able to defend space spreads a greater distance (‘confrontational strategy’) from origin (fugitive strategy) Friday, 7 October 2011 Percentage of SHALLOW DEEP (> 50 m) colony-forms in bryozoan assemblages from shallow and deep 14% 21% stations in Spitsbergen 74% Uniserial 77% Multiserial encrusters encrusters ?reflecting decreasing food resources with depth Friday, 7 October 2011 Fenestrate colonies Cheilostome 'Sertella' (reteporiform) (Oligocene, Argen'na) • 'traditionally' regarded as adaptation to strong currents • but colonies can be found in slow flow regimes too (e.g. caves) Chasmatopora (Ordovician, Estonia) Friday, 7 October 2011 Arculated colonies Cheilostome Cellaria (Recent, Croaa) (cellariiform) • elastic nodes allow flexure in strong currents • but colonies also found in areas of relatively high sedimentation and weak currents – sediment can be shaken off branches Crisia (Recent, Brazil) Friday, 7 October 2011 Free living colonies (lunuliform) Cupuladria Cupuladria (Pliocene, England) (Miocene, France) • able to live on fine sediments (fine sand, silt and mud) where no large substrates are present • colonies can dig themselves out if buried Friday, 7 October 2011 adapted for living on fine-grained, unstable substrates Friday, 7 October 2011 Dome shaped: 'Dianulites' Encrusng: Porella Foliose: Pentapora Fenestrate: Chasmatopora Arculated: Cellaria Free-living: Cupuladria Palmate: Phaenopora Robust branched: Heteropora Narrow branched: Arcanopora Friday, 7 October 2011 Changing proportion of bryozoan colony-forms through time ORD SIL DEV CARB PERM TRI JUR CRET PG NG Friday, 7 October 2011 Using bryozoan colony-form in palaeoenvironmental reconstruction must be approached with caution Friday, 7 October 2011 Using bryozoan colony-form in palaeoenvironmental reconstruction must be approached with caution • particular colony-forms are seldom if ever restricted to one environment; sometimes almost all major colony-forms can be found together Friday, 7 October 2011 Using bryozoan colony-form in palaeoenvironmental reconstruction must be approached with caution • particular colony-forms are seldom if ever restricted to one environment; sometimes almost all major colony-forms can be found together • not enough known about factors controlling colony-forms in modern environments Friday, 7 October 2011 Using bryozoan colony-form in palaeoenvironmental reconstruction must be approached with caution • particular colony-forms are seldom if ever restricted to one environment; sometimes almost all major colony-forms can be found together • not enough known about factors controlling colony-forms in modern environments • colony-forms represent alternative functional adaptive strategies that may be viable in many different environments Friday, 7 October 2011 Using bryozoan colony-form in palaeoenvironmental reconstruction must be approached with caution • particular colony-forms are