concentrations of oxygen and high concentrations of nutrients (Zuta and
Guillén 1970; Strub et al. 1998).
The arrival of these nutrients to the surface generates intense primary
productivity of around 1 kg C m
-2 y
-1 (Tarazona et al. 2003). The high abundance of plankton is the base of a trophic chain where the Peruvian anchoveta
(Engraulis ringens) is the dominant species and the primary food of enormous
populations of guano birds whose droppings (guano) are accumulated over the
islands and capes. Wind action spreads some of the guano, fertilizing the marine
waters even more (Palomares et al. 1987).
The influence of the upwelling reaches up to a depth of 100 km out into the
ocean (Tarazona et al. 2003). Its influence is also reflected in coastal waters.
The nutrients allow great beds of brown macroalgae as well as other algae to
develop. They are used by herbivorous organisms, such as several species of sea
urchins and gastropod mollusks.
Nevertheless, the primary productivity does not always favor the abundance of
organisms. In the area occupied by the Peruvian Current, oxygen decreases
rapidly, reaching hypoxic conditions (\1 ml l
-1 ) at depths below 20 m (Rosenberg et al. 1983). In waters between 100 m and 500 m in depth, oxygen concentration usually is almost zero (\0.1 ml l
-1 ) so diversity there is at a minimum.
The cause is the great abundance of plankton in surface waters that, after death,
generate a constant organic rain that decomposes as it sinks. The bacterial activity,
both in the water column as well as over the organic sediments accumulated on the
sea bottom, consumes the dissolved oxygen and generates a minimum oxygen
layer that extends the length of the Peruvian Current (Lama et al. 2009).
Outside the continental shelf oxygen reappears in the water column at depths
below 50 m carried by the Subsurface Peruvian Current. Over the bottom, at
600 m, biological diversity increases, reaching higher values at 1,000 m in depth,
where oxygen-rich Antarctic Intermediate Waters occur (Lama et al. 2009).
In northern Peru, the tropical oceanographic conditions result in totally different
ecological characteristics than those occurring south of 6°S. Tropical currents
coming from the north maintain surface temperatures at coastal areas usually
between 20 and 25 °C (Fig. 8.2). This allows the establishment of a purely tropical
ecosystem with a high diversity. Hooker (2009) indicates they include more than
70 % of the total richness of the Peruvian littoral at shallow depths. This region,
especially in the northern tip close to the border with Ecuador, is the only place
where the influence of low salinity waters is significant due to the great volume of
freshwater coming from Ecuadorian rainy areas, generating mangrove forests
between the delta of the Tumbes River and the Zarumilla River that mark the
border with Ecuador. Sediments carried out by these rivers also influence coastal
diversity because waters become murky close to the mouths of the rivers.
The effect of suspended sediment is dissipated to the South, where clearer waters
are found between 3°52
0 and 4°15
0 S. Species richness increases, especially on
rocky reefs. It should be pointed out that Peruvian marine waters do not have any
coral reefs and there is only one record of a hermatypic coral species.
282
Y. Hooker et al.
Guillén 1970; Strub et al. 1998).
The arrival of these nutrients to the surface generates intense primary
productivity of around 1 kg C m
-2 y
-1 (Tarazona et al. 2003). The high abundance of plankton is the base of a trophic chain where the Peruvian anchoveta
(Engraulis ringens) is the dominant species and the primary food of enormous
populations of guano birds whose droppings (guano) are accumulated over the
islands and capes. Wind action spreads some of the guano, fertilizing the marine
waters even more (Palomares et al. 1987).
The influence of the upwelling reaches up to a depth of 100 km out into the
ocean (Tarazona et al. 2003). Its influence is also reflected in coastal waters.
The nutrients allow great beds of brown macroalgae as well as other algae to
develop. They are used by herbivorous organisms, such as several species of sea
urchins and gastropod mollusks.
Nevertheless, the primary productivity does not always favor the abundance of
organisms. In the area occupied by the Peruvian Current, oxygen decreases
rapidly, reaching hypoxic conditions (\1 ml l
-1 ) at depths below 20 m (Rosenberg et al. 1983). In waters between 100 m and 500 m in depth, oxygen concentration usually is almost zero (\0.1 ml l
-1 ) so diversity there is at a minimum.
The cause is the great abundance of plankton in surface waters that, after death,
generate a constant organic rain that decomposes as it sinks. The bacterial activity,
both in the water column as well as over the organic sediments accumulated on the
sea bottom, consumes the dissolved oxygen and generates a minimum oxygen
layer that extends the length of the Peruvian Current (Lama et al. 2009).
Outside the continental shelf oxygen reappears in the water column at depths
below 50 m carried by the Subsurface Peruvian Current. Over the bottom, at
600 m, biological diversity increases, reaching higher values at 1,000 m in depth,
where oxygen-rich Antarctic Intermediate Waters occur (Lama et al. 2009).
In northern Peru, the tropical oceanographic conditions result in totally different
ecological characteristics than those occurring south of 6°S. Tropical currents
coming from the north maintain surface temperatures at coastal areas usually
between 20 and 25 °C (Fig. 8.2). This allows the establishment of a purely tropical
ecosystem with a high diversity. Hooker (2009) indicates they include more than
70 % of the total richness of the Peruvian littoral at shallow depths. This region,
especially in the northern tip close to the border with Ecuador, is the only place
where the influence of low salinity waters is significant due to the great volume of
freshwater coming from Ecuadorian rainy areas, generating mangrove forests
between the delta of the Tumbes River and the Zarumilla River that mark the
border with Ecuador. Sediments carried out by these rivers also influence coastal
diversity because waters become murky close to the mouths of the rivers.
The effect of suspended sediment is dissipated to the South, where clearer waters
are found between 3°52
0 and 4°15
0 S. Species richness increases, especially on
rocky reefs. It should be pointed out that Peruvian marine waters do not have any
coral reefs and there is only one record of a hermatypic coral species.
282
Y. Hooker et al.