HARBOR UPDATE

Transfer of Nut Island flows, and changes inthe water quality of Boston Harbor

David Taylor

9

NITROGEN LOADINGS TO BOSTON HARBOR

Boston Harbor receives loadings of total nitrogen (TN) from terrestrial plus atmospheric sources of 6.6 x 105 kmol y-1 (Kelly 1998).

This is among the highest reported for any bay or estuary in the USA (Kelly 1991, Nixon et al. 1996).

>90% of these inputs occur from wastewater (Alber and Chan 1994).

9

SYMPTOMS OF EUTROPHICATION

Elevated nutrient concentrations (Kelly 1998) and phytoplankton biomass (HydroQual 1994)

Almost total demise of seagrass beds, and heavy epiphytization of remaining beds (Colaruso, EPA)

Low dissolved oxygen concentrations in Inner Harbor (MWRA unpubl. data)

Supports benthic invertebrate communities typical of moderately degraded environments (Blake et al. 1998).

1996 1997 1998 19990

200

400

600

800

1000

Start and completion dates

Nut Is.

Deer Is.

FL

OW

(m

gd)

1996 1997 1998 19990

200

400

600

800

1000

SecondaryBattery B

SecondaryBattery A

Nut Is.

Deer Is.

FLO

W (

mgd

)

9

CONCLUSIONS

Changes in water quality have been observed in Boston Harbor since transfer of Nut Island flows.

The South Harbor has shown decreased concentrations of DIN, increased water clarity, and variable responses of biomass of phytoplankton.

The North Harbor has shown increased DIN concentrations, a small increase in clarity at the outfalls, and no change in phytoplankton biomass.

The phytoplankton responses to increased nitrogen loadings appear to have been manifested in west Mass Bay.

1996 1997 1998 1999

0

20

40

60

80

100

AVERAGE MONTHLY FLOWS SECONDARY TREATED (%)

%SecondaryBattery B

SecondaryBattery A