2. 1.3.2. Thermohaline and optical properties of the Drvenik-Hvar-Pelješac area Branka Grbec 1 (thermohaline), M ira Morović 1* (optical), Frano Matić 1, Vlado Dadić 1, Igor Palandžić 2 1-Institute of Oceanography and Fisheries, Split, Croatia 2-Hydraulical Institute, Sarajevo, Bosnia and Herzegovina

4. PROFILE A 2002-2003

5. PROFILE B 2002-2003

6. PROFILE C – NERETVA ESTUARY 2002-2003

7. July 2006 Strong heating caused sea temperatures above 26 o C. Low impact of less saline coastal waters at the surface. Shallow thermocline, because of the absence of stronger winds.

8. July 2006 Strong heating Low salinity water (salinity < 34) occupied surface layers in the most southward part of the area.

9. Thermocline depth was fully developed, below 20 m. Impact of freshwater at the surface lower than in June. September 2006

10. Conditions during September cruise were stable with more uniform spatial distribution of temperature and salinity with respect to July.

14. High resolution measurements of downward irradiance and upward radiance at 14 wavelengths from UV to visible light (340; 380; 412; 443; 465; 490; 510; 532; 555; 589; 625; 665; 683; 710); PAR attenuation (400-700nm); fluorescence K d =dln(E d (z))/dz K u =dln(L u (z))/dz K Par = dln(E Par (z))/dz Processing: 1.Determining cast options 2.Selection of better cast for each measurement 3.Dark callibration 4.Calculations

15. 1. Qualitative and quantitative analysis of spectrum 2. Changes with depth 2. Attenuation coefficients for every wavelength and for PAR 3. Amount of light available for photosynthesis 4. Euphotic zone depth 5. Optical signature of chlorophyll-like pigments (for comparison of chlorophyll signature from remote sensing) 6. Estimates of concentration of chlorophyll-like pigments 7. Estimation of optical types 8. Estimation of different optical functions

20. PAR irradiance (%) relative to the subsurface in July and September

21. PAR attenuation coefficients in July and September

23. July September

24. Figure 10. Estimated concentration of chlorophyll-like pigments in July (left) and September (right). Estimates of chlorophyll-like pigments concentrations for July and September 2006 In September, relative to July, the stations close to Klek-Neum Bay, in the surface 10meters, have for the order of magnitude higher estimates of chlorophyll

25. Chlorophyll from MODIS for July and September AVHRR temperature

26. According to water characterisation by Matić (2004), the three characteristic sub-regions can be distinguished: 1. Neretva River estuary (St11-St23) - surface layer of permanently low salinity but spatially and temporally changeable under local meteorological conditions; 2. channel waters (St01-St03, St07-St08) – low salinity surface water influenced by the three main rivers: Neretva, Cetina and Jadro; and 3. waters similar to the open sea (St04-St06) without considerable influence from river runoff and vertically well mixed in the cold period of year. Stations from waters similar to the open sea have different spectrum characteristics from stations of the Neretva river estuary (Klek-Neum area); spectrum max intensity for estuary area is shifted towards longer wavelengths. Higher attenuation coefficients (for PAR and wavelengths) in September than in July especially in the Klek-Neum area Higher chlorophyll-like pigments concentrations estimated for September especially at the surface for most stations, than for July, especially in the Klek- Neum area Optical characteristics are related to thermohaline characterisation Concluding remarks