Transcript mb3ech06-b - Chaparral Star Academy

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 of
the herring
in 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 of
snail Cymatium parthenopetum
Pluteus larva of an urchin
PROBLEM OF SWIMMING LARVAE:
water motion carries them away from
appropriate habitats
Loss to offshore waters
Wind-driven
recruitment
onshore
Self-seeding
eddies
Longshore drift
Shore Population
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 the
ebbing tide: results in retention of larvae within estuary
Falling
Rising
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
Consuelo Montero
Concholepas concholepas see Poulin et al.
Limnology Oceanography 47:1248-55 (2002)
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
Expectation of life
(months)
• Energetic cost of metamorphosis
• Predation
• Crowding --> mortality
Initial
6 months
12 months
18 months
Interindividual contacts per cm 2
Expectation of life of Semibalanus balanoides as function of crowding
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)
Instructor: Recommend that you find images from the
site below
Nauplius
(feeding)
Barnacle larvae
http://www.microscopy-uk.org.uk
Cypris (nonfeeding)
Why disperse?
• Local extinction - to export young
• Hedging bets - spread over habitats
• Not for dispersal! Feeding in plankton
The End