1. International Estuaries
“Different Places but the Same Theme”

2. Overview Estuary function is the same world-wide
Outside of estuaries in the United States, international estuaries are just as diverse
We will focus on an estuary in each of the major continents (an example and some key factors)
These factors will include: geology, physical characteristics and unique biological interactions

3. An Estuary Down Under - Swan River
Key Characteristics: Is considered a tide-dominated estuary with tidal ranges up to 4 meters There has been a decrease in freshwater flow into the main opening of the estuary It is divided into the upper, middle and lower estuarine areas (Neira et al. 1992)

5. Swan River
There are significant seasonal effects on this estuary in terms of salinity
The lower part of the estuary can range in salinity from 35 PPT to 5 PPT (depending on the weather episode - drought vs. monsoonal patterns)
Over 80% of the larval species spawn in marine waters

6. Swan River
The hydrology changed back in the early 1900s when it was dredged closer to the mouth of the estuary, thus allowing a greater push of salt water up river
Hamilton et al. 2001

7. Swan River
As a result of the infiltration of Indian Ocean water into Swan River, there is a salt wedge that forms (but it is not well mixed)
It was classified as meso/ eutrophic back in the 1990’s
Development pressure and urban sprawl are contributing factors to the changes (in Hamilton et al. 2001)

8. Swan River Changes in the salt wedge vary greatly each season...
The dry summer months allow for intrusion of the high salinity water to 50 km
The wet months (winter)push less-salty water toward the mouth of the river with a salt wedge influence between 5 and 20 km
A “typical tidal influence would be 2 – 3 km”

9. The increase in salinity…
Swan River study taken at the barge site (Hamilton et al. 2001).

10. What does this mean? There are changes in the hydrology of Swan River
These changes produce a salt-wedge with a bottom layer that is lower in dissolved oxygen
Also, the increase in salt water upstream, seasonally, impacts the phytoplankton communities (shifts in primary productivity levels)
A better look at the Swan River

11. A European Estuary – Venice, Italy
Lazzari et al. 2004

12. Venice – a series of canals
Image NASA.gov (aerial image of the Venice Estuary)

13. Venice (Venezia)
The Dese Estuary is one of the lagoons of Venice, Italy – it is the largest in all of Italy (Maggiore and Keppel 2007)
As a result of its location in the northern part of the Adriatic Sea, confinement is a key aspect for biological organisms and water quality
There are four basins in Venice and three inlets that provide exchange to the Adriatic Sea (Solidoro et al. 2004)

14. Venice
Bathymetry of the estuary of Venice as it opens into the North Adriatic Sea.
Roland et al. 2009

15. Venice
Tidal fluxes based on location in N. Adriatic Sea (Roland et al. 2009)

16. Venice
Storm surge at Venice based upon wave height and movement of water into the upper Adriatic Sea
Roland et al. 2009

17. Venice A city with sea level issues (here)
Human influences go back hundreds of years and include constant management, thus “human-caused” introduction of species
There are over 30 species alone that are considered invasive (Ambrogi 2000).

18. Venice
“Crassostrea gigas (Pacific oyster) and the clam Tapes philippinarum have been imported in the lagoon in order to replace two species of bivalves that had undergone severe reductions in population” (Occhipinti-Ambrogi and Savini 2004)

19. The invasive cycle…
The introduced Pacific oyster has led to a shift in the algal community…
Here are some non-native algae species that are taking over the canals throughout Venice… Undaria pinnatifida, Sargassum muticum and Antithamnion pectinatum

20. Some of the invasive algal types

21. Managing Venice
There are efforts to reduce non-native species including invertebrates like bryozoans that are tolerant to the lower salinities
Sea level rise a major threat and recognizing flooding threats are a priority
A healthy system can reduce the threat on non-native and invasive species

22. Tijuana Estuary, Mexico
Primarily a shallow water habitat, though it is often termed an "intermittent estuary," as it is subjected to extreme changes in streamflow at different times of the year (National Estuary Program, 2008).
Changes in the tidal flow have caused a decline in diversity of species in that the habitat has been altered much like 90 percent of the wetlands habitat across southern California (Zedler et al., 2001)

24. Tijuana
As a result of increased salinity, it is considered a negative estuary
Extreme hypersalinity from is more characteristic of higher elevations with less frequent tidal inundation (Noe and Zedler, 2001).
Decrease in freshwater inputs and changes in seasonal weather patterns, the Tijuana watershed has been drier and the mean salinity has increased (see the following figure from Zedler et al., 2001).

27. Tijuana Estuary
In comparison to other estuarine systems, the lack of outflow water creates a high percentage of hypoxia in the Tijuana estuary, 25.2% – 30.2% (Wenner et al. 2004)
In southern California, prior to development, approximately seven creeks and river tributaries provided freshwater flows into the San Diego Bay.

28. How would you help the estuary?
Please discuss how you would aid an estuary that has negative estuary characteristics….