Table T3. Species compositon and related environmental preferences of the seven diatom groups, Site 1077.

Diatom group
composition (average %)
Environmental conditions
Freshwater 2.7 Related to the Congo River discharge
Aulacoseira spp. 64.0
Marine 97.3

Low salinity 18.8 Related to the Congo River plume
Cyclotella litoralis

High nutrients 64.0
Chaetoceros spp 24.2 Highly productive waters where river-induced upwelling is inferred
Thalassionema nitzschioides var. nitzschioides 39.8 Highly productive nearshore waters to the north of the river plume nearshore
Neritic 11.0
Actinocyclus aff. curvatulus

Actinocyclus octonarius

Coscinodiscus radiatus

Rhizosolenia setigera/pungens

Skeletonema costatum

Thalassiosira angulata

Thalassiosira eccentrica

Littoral 0.7 Transported from the shelf
Actinoptychus senarius

Actinoptychus vulgaris


Warm 1.7 Related to the warm, high saline waters of the SECC with low nutrient levels
Alveus marinus

Asteromphalus flabellatus

Azpeitia nodulifera

Nitzschia interruptestriata

Planktoniella sol

Pseudosolenia calcar-avis

Rhizosolenia bergonii

Thalassionema nitzschioides var. parva

Thalassionema nitzschioides var. inflatula

Thalassiosira ferelineata

Thalassiosira lineata

Thalassiosira simonsenii

Oceanic temperate 3.2 Related to cold, nutrient-rich waters of the BCC, probably reflecting northward movement of the ABF
Bacteriastrum elongongatum/furcatum

Fragilariopsis doliolus

Thalassiosira oestrupii var. oestrupii

Notes: Data are based on observations of van Iperen et al. (1987), Pokras and Molfino (1986), and Romero et al., (1999a). SECC = South Equatorial Countercurrent, BCC = Benguela Coastal Current, ABF = Angola Benguela Front.