Based on empirical relations found in the literature, relatively simple mathematical models of the average of the total absorption of seawater [a(T(z,Chl))], the chlorophyll-specific absorption coefficient of phytoplankton [a*(ph(z,Chl))], and the backscattering coefficient [b(b(Chl))], weighted by the in situ spectral distribution of photosynthetically active scalar irradiance (PAR), as functions of chlorophyll concentration and depth, were developed. The models for a(T(z,Chl)) and b(b(Chl)) can be used to calculate the coefficient of vertical attenuation of PAR [K(o(z,Chl))] and therefore to estimate the vertical profile of PAR as an input to algorithms for primary production. One application of a*(ph(z,Chl)) may be in the correction of the initial slope of the photosynthesis-irradiance curve [alpha*((z))] for the in situ spectral distribution of PAR and the package effect. Also, a*(ph(z,Chl)) may be used to calculate phi((z)), the in situ quantum yield of photosynthesis, from phi(max) and irradiance.

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Water exchange between the Gulf of California and the Pacifi c has a signifi cant vertical component. Surface (0 -200 m) gulf water fl ows out into the Pacifi c, and deep (200 -600 m) water fl ows into the Gulf. We propose a biogeochemical method to estimate the vertical component of water exchange assuming a steady state for the concentration of nutrients in the Gulf and using the annual input of dissolved Si needed to support the production of opal accumulated in its sediments. An estimated average opal accumulation of (273.3 ± 6.8, mean ± SE)×10 9 mol SiO 2 year -1 for the whole Gulf was extracted from literature sources. Annual averages for H 4 SiO 4 , at the mouth of the Gulf and for the depth intervals 0 -200 m and 200 -600 m, were used to calculate the annual average vertical component of water exchange between the Gulf and the Pacifi c needed to balance this opal accumulation, i.e., 0.23 ± 0.02 Sv. This relatively low value is only ∼ 3 % of the whole average water exchange. This vertical component value was used to calculate the net annual nitrate input from the Pacifi c into the Gulf, and with the Redfi eld ratio it was transformed to new phytoplankton production for the whole Gulf [(10.67 ± 3.66)×10 9 kg C year -1 ].

The universal bio-optical algorithm of the Coastal Zone Color Scanner (CZCS) for case I waters implicitly contains an average covariance of the absorption by phytoplankton and colored dissolved organic matter (CDOM) and detritus. We made that covariance explicit by combining the CZCS algorithm with an expression for reflectance. The spectral variation of absorption by CDOM plus detritus for case I waters may be estimated by the expression a(gd(λ)) = 2a(ph)(443)*chl{exp[-0.013(λ - 443)].