Movement of Marine Organisms. Dispersal versus Migration DISPERSAL: UNDIRECTED MIGRATION: DIRECTED,...
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Transcript of Movement of Marine Organisms. Dispersal versus Migration DISPERSAL: UNDIRECTED MIGRATION: DIRECTED,...
Movement of Marine Organisms
Dispersal versus Migration
DISPERSAL: UNDIRECTED
MIGRATION: DIRECTED, RETURN SPECIFIC
Migration Scheme
Migration Types
• ANADROMOUS - fish live as adults in salt water, spawn in fresh water (shad, striped bass), more common in higher latitudes
• CATADROMOUS - fish live as adults in fresh water, spawn in salt water (eel), more common in lower latitudes
• DIADROMOUS = ANADROMOUS + CATADROMOUS
• FULLY OCEANIC - herring, green turtle
Migration
Geographic specificity of migration - non-specific in some, very specific in others (green turtle, oceanic salmon)
Migration ofthe herringin the North
Sea
EEL MIGRATIO N - (European: Anguilla anguilla; American: Anguilla rostrata
Larval Dispersal
Dispersal Types in Benthic Species
• PLANKTOTROPHIC DISPERSAL - female produces many (103 to 106) small eggs, larvae feed on plankton, long dispersal time (weeks), some are very long distance (teleplanic) larvae - cross oceans
• LECITHOTROPHIC LARVAE - female produces fewer eggs (102 to 103), larger, larvae live on yolk, short dispersal time (hrs to days usually)
• DIRECT RELEASE - female lays eggs or broods young, juveniles released and crawl away
• Combinations of above? Yes, but rare
Lecithotrophic larva: tadpole larva of the colonial ascidian Botryllus schlosseri
Planktotrophic larva ofsnail Cymatium parthenopetum
Pluteus larva of an urchin
PROBLEM OF SWIMMING LARVAE:water motion carries them away fromappropriate habitats
Shore Population
Longshore drift
Loss to offshore waters
Self-seedingeddies
Wind-drivenrecruitment
onshore
Internal waves, tidal bores
Effect of local eddies on larval retention in a patch reef on the Great Barrier Reef, Australia
Two modes of beginning of larval life
Estuarine larval adaptations - Retention
Larvae rise on the flooding tide, sink to bottom on theebbing tide: results in retention of larvae within estuary
Rising
Falling
Fiddler Crabs - Lopez and Tankersley 2007
Estuarine larval adaptations - movement of larvae to coastal waters, return of later stage larvae
Blue crab, Callinectes sapidus
Epifanio and Garvine 2001
Estuarine and Coastal Shelf Sci.
v. 52: 51-77
1. Estuarine flow, southward transport
2. Mixing northward, upwelling
3. Mixing onshore from southward winds, Aug-Sept
Larvae onto the Shelf - the Fatal Blow?
• Estuarine loss to shelf - can they come back?
• Upwelling - loss of larvae to open sea?
Estuarine Loss - Problem of Loss from Estuarine Flow
Buoyant flow - larvae leave estuaries for open sea, good to allow larvae to feed on plankton on shelf, perhaps to avoid predation. But will they ever come back?
Possible solution - seasonal alternation of buoyant flow combined with upwelling favorable winds (summer) and shoreward favorable winds later in August and fall, bringing larvae toward shore
Natunewicz et al. 2001 Marine Ecology Progress Series 222:143-154
Blue crab Callinectes sapidus
Upwelling - Guaranteed loss?
• Relaxation of upwelling
• Upwelling moves toward shore
• Larvae sink below surface upwelling waters
Concholepas concholepas see Poulin et al. Limnology Oceanography 47:1248-55 (2002)
Consuelo Montero
Settling Problems of Planktonic Larvae
• Presettling problems:
Starvation
Predation in plankton
Loss to inappropriate habitats
Example of Effect of Starvation:Phytoplankton variation and barnacle larval success
Semibalanus balanoides settlement in a Scottish Sea Loch
Postsettling Problems• Energetic cost of metamorphosis
• Predation
• Crowding --> mortality
Expectation of life of Semibalanus balanoides as function of crowding
Interindividual contacts per cm2
Exp
ecta
tion
of
life
(mon
ths)
Initial6 months12 months18 months
Two Scales of Larval Dispersal and Settlement
1. Large scale - 10-103 km
Small scale movements to take advantage of currents, seasonal release and settlement
2. Smaller scale - 10-2 - 102 m
Positive, neg phototaxis, timing, near cues (< 10-1 m)
Stages in the selection of substratum by planktonic larvae
Stages:
Larvae are competent
Larvae seek bottom (photo+ photo-, timing) (Melampus bidentatus)
Larvae seek further cues
Substratum - cracks, shade
Gregarious settling - members of own species - chemical cues (oysters: peptide, Hydroides sp.), very short distances - mm
Settling on other species (Proboscidactylidae, bryozoans)
Larvae make final movements - find local spot, space from others (Spirorbis), currents good for adults (barnacle larvae)
Barnacle larvae
Nauplius (feeding) Cypris (non-
feeding)
http://www.microscopy-uk.org.uk
Instructor: Recommend that you find images from the
site below
Why disperse?
• Local extinction - to export young
• Hedging bets - spread over habitats
• Not for dispersal! Feeding in plankton
The End