Upwelling and Lagoonal Ecosystems of the Dry Pacific Coast of Baja California
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phytoplankton community of the California Current ecosystem is characterized by an assemblage of diatoms ( Chaetoceros decipiens, Rhizosolenia
robusta, R. styliform is, Skeletonema costatum, Asterionella japonica, Thalassionema nitzschiodes), dinoflagellates ( Ceratium extensus, Peridinium
sp., Gonyaulax catenella, G. polyhedra), and coccolithophores (Umbilicosphaera sibogae). Chaetoceros and Rhizosolenia (up to 40%) tend to dominate nutrient-rich waters where they compete with Asterionella while Skeletonema appears to prefer moderate nutrient concentration, and thus
blooms at different times than Chaetoceros and Asterionella. Dinoflagellates, with Ceratium as the dominant genus, bloom profusely when surface
waters are warm in the summer or when warm water masses are mixed
with California Current waters. Protozoans are largely represented by
planktonic ( Globigerina bulloides, Globigerinoides ruber) and benthic
foraminifera (Buliminella elegantissima, Elphidium translucens, Quinqueloculina costata), radiolaria (Stylatractus spp., Acanthastaurus spp.), and
tintinnidae ( Tintinnus fraknoii).
The zooplankton in shallow waters (<100m) off Baja California is dominated by copepods (Euchaeta media, Temora discaudata, Rhincalanus
nasutus, Pleurommamma gracilis). Deeper waters (>200m) are typical of
Calanus pacificus and C. californicus, euphausids (Nyctiphanes simplex,
Euphasia eximia, E. brevis, E. hemigibba), caetognaths (Sagitta bierii, S.
euneritica, S. minima), the pteropod Limacina inflata, the decapod Pleuroncodes planipes, the salp Thalia democratica, and squid and fish larvae
(Vinciguerria lucetia). Most of these species are herbivores, such as the
euphasiids (which rank second to copepods in abundance), while others,
such as chaetognaths (also commonly known as arrowworms), are predators and feed mostly on copepods and other small zooplankton. In general, tropical oceanic populations (e.g., Euchaeta sp.) dominate the epipelagic layer of the water column while deeper water populations are
dominated by temperate species (e.g., Calanus sp.).
Micronekton in the California Current is composed of cephalopods
(Abraliopsis felis, Loligo opalescens), myctophid (lantern) fishes (Triphoturus mexican us, Stenobrachius leucopsarus), Pacific saury ( Cololabis saira),
rockfishes (Sebastes macdonaldi), cnidarians (Liriope tetraphyla, Rhopalonema velatum), and pelagic shrimps (Sergestes similis). An inverse relation
between larvae of medusae and anchovies suggests that medusae prey
upon anchovies. Also, adults of the shrimp Sergestes similis most often prey
on larvae of fish but are a favorite prey for the squid Loligo opalescens.
Copepods and euphasids are ingested by lantern fishes, which follow their
vertical diurnal migrations, and by the Pacific saury; thus, these species
represent an important link between zooplankton and high-level carnivores such as tuna, squid, billfishes, seabirds, sharks, seals, and whales.
319
phytoplankton community of the California Current ecosystem is characterized by an assemblage of diatoms ( Chaetoceros decipiens, Rhizosolenia
robusta, R. styliform is, Skeletonema costatum, Asterionella japonica, Thalassionema nitzschiodes), dinoflagellates ( Ceratium extensus, Peridinium
sp., Gonyaulax catenella, G. polyhedra), and coccolithophores (Umbilicosphaera sibogae). Chaetoceros and Rhizosolenia (up to 40%) tend to dominate nutrient-rich waters where they compete with Asterionella while Skeletonema appears to prefer moderate nutrient concentration, and thus
blooms at different times than Chaetoceros and Asterionella. Dinoflagellates, with Ceratium as the dominant genus, bloom profusely when surface
waters are warm in the summer or when warm water masses are mixed
with California Current waters. Protozoans are largely represented by
planktonic ( Globigerina bulloides, Globigerinoides ruber) and benthic
foraminifera (Buliminella elegantissima, Elphidium translucens, Quinqueloculina costata), radiolaria (Stylatractus spp., Acanthastaurus spp.), and
tintinnidae ( Tintinnus fraknoii).
The zooplankton in shallow waters (<100m) off Baja California is dominated by copepods (Euchaeta media, Temora discaudata, Rhincalanus
nasutus, Pleurommamma gracilis). Deeper waters (>200m) are typical of
Calanus pacificus and C. californicus, euphausids (Nyctiphanes simplex,
Euphasia eximia, E. brevis, E. hemigibba), caetognaths (Sagitta bierii, S.
euneritica, S. minima), the pteropod Limacina inflata, the decapod Pleuroncodes planipes, the salp Thalia democratica, and squid and fish larvae
(Vinciguerria lucetia). Most of these species are herbivores, such as the
euphasiids (which rank second to copepods in abundance), while others,
such as chaetognaths (also commonly known as arrowworms), are predators and feed mostly on copepods and other small zooplankton. In general, tropical oceanic populations (e.g., Euchaeta sp.) dominate the epipelagic layer of the water column while deeper water populations are
dominated by temperate species (e.g., Calanus sp.).
Micronekton in the California Current is composed of cephalopods
(Abraliopsis felis, Loligo opalescens), myctophid (lantern) fishes (Triphoturus mexican us, Stenobrachius leucopsarus), Pacific saury ( Cololabis saira),
rockfishes (Sebastes macdonaldi), cnidarians (Liriope tetraphyla, Rhopalonema velatum), and pelagic shrimps (Sergestes similis). An inverse relation
between larvae of medusae and anchovies suggests that medusae prey
upon anchovies. Also, adults of the shrimp Sergestes similis most often prey
on larvae of fish but are a favorite prey for the squid Loligo opalescens.
Copepods and euphasids are ingested by lantern fishes, which follow their
vertical diurnal migrations, and by the Pacific saury; thus, these species
represent an important link between zooplankton and high-level carnivores such as tuna, squid, billfishes, seabirds, sharks, seals, and whales.