Environmental Factors Relevant to Eelgrass in the Neponset River Estuary Christina Ciarfella Map 1. Area of Neponset River estuary evaluated and used for.

Environmental Factors Relevant to Eelgrass in the Neponset River Estuary

Christina Ciarfella

Map 1. Area of Neponset River estuary evaluated and used for calculations

SalinitypH

Temperature

Wave Action

Light Intensity

Flow Rate

Substrate

Dissolved Oxygen

InhibitorsTurbidity

Nitrogen

Grazers

SalinitypH

Temperature

Wave Action

Light Intensity

Flow Rate

Substrate

Dissolved Oxygen

InhibitorsTurbidity

Nitrogen

Grazers

Methods

• Processed MWRA physical data• Calculated light intensity using MWRA secchi

depths• Estuary Loading Model (NLOAD)• Processed MWRA chlorophyll a data• Reviewed literature and class assessments

Source: MWRA website

Map 1. Area of Neponset River estuary evaluated and used for calculations

Seasonsal Temperature by Year

1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 20110

5

10

15

20

25

Figure 1: Seasonsal Temperature by Year in Neponset River Estuary

Jan-MarApr-JunJul-SepOct-Dec

Year

Tem

pera

ture

oC

Error bars are +/- 1 σ

Seasonsal Salinity by Year

1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 20110

5

10

15

20

25

30

35

Figure 2: Seasonsal Salinity by Year in Neponset River Estuary

Jan-MarApr-JunJul-SepOct-Dec

Year

Salin

ity (P

SU)

Seasonal pH by Year

1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 20110

1

2

3

4

5

6

7

8

9

Figure 3: Seasonsal pH by Year in Neponset River Estuary

Jan-MarApr-JunJul-SepOct-Dec

Year

pH

Error bars are +/- 1 σ

Seasonsal Dissolved Oxygen by Year

1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 20110

2

4

6

8

10

12

14

Figure 4: Seasonsal Dissolved Oxygen by Year in Neponset River Estuary

Jan-MarApr-JunJul-SepOct-Dec

Year

Diss

olve

d O

xyge

n (m

g/L)

Seasonsal Turbidity by Year

1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 20110

5

10

15

20

25

30

35

Figure 5: Seasonsal Turbidity by Year in Neponset River Estuary

Jan-MarApr-JunJul-SepOct-Dec

Year

Turb

idity

(NTU

)

Table 2: Estimated Light Intensity

Station

Secchi depth (m) Site depth (m) Light intensity at

site depth (E/day)

39 1.56 3.94 1.32

40 1.56 2.96 3.84

41 1.44 5.90 0.10

42 1.19 5.80 0.02

54 0.98 6.02 0.003

84 1.69 6.46 0.15

89 1.19 2.12 4.77

140 1.89 8.25 0.058

Beers-Lambert Equation

Id = I0e-kd

Id = light intensity at site depth

I0 = light intensity at the surface

k = attentuation coefficient (1.7/secchi depth)

d = site depth

Light Intensity

*Id must equal 6.4-12.9E/day for growth

Estuarine Loading Modal

Input Estimation Method/Source

Land and freshwater derived TDN load (kg per year) 820786.52 Output from NLM Model (phase 1 assessment nload.mbl.edu)

Open water area (ha) 217 Considered to be the same as surface area at high tide; data from Gardner, Chen & Berry 2005, via Lynn's AP1

Average depth (m) 4.21 Averaged all bottom depths within and between sites from MWRA physical data 1994-2011 (mwra.state.ma.us )

Tidal range (m) 3 Zhu & Olsen 2009 via Lynn's AP1

Tidal period (hrs per day) 6 Boston Tide Charts (boatma.com/tides)

Number of houses 259827 334.4 houses per square mile, converted to square km, multiplied by 300 km2 (census-charts.com)

Salt marsh area (ha) 107.513 Tiner et al. 1998; via Lynn's AP1

Eelgrass bed area (ha) 0 Eelgrass Mapping Project Viewer (mass.gov)

Total watershed area (ha) 33669.8 neponset.org/Watershed.htm

Length of estuary perimeter (m) 16000 Visual estimation using GIS (maps.google.com)

Flushing time of the freshwater reach (days) 0.063

Used the relative surface areas over tidal range (Gardner, Chen & Berry 2005, via Lynn's AP1) to calculate slope; assumed estuary was conic to calculate volume; used volume over flow rate to calculate flushing time.

Output: Net DIN loading in estuary is 666413.3kg N/year

1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 20110

2

4

6

8

10

12

14

Figure 6: Seasonsal Chl a by Year in Neponset River Estuary

Jan-MarApr-JunJul-SepOct-Dec

Year

Chlo

roph

yll a

(µg/

L)

Error bars are +/- 1 σ

Inhibitors: phytoplankton & macroalgae

http://birdway.com.au/anatidae/black_swan/source/black_swan_85609.htm

Potential Grazers

• Mute swan• Brant goose• Mallard• Wigeon• Pintail• Coot• Blue crab• Marsh crab • Amphipods• Isopods• Chink snail• Sea slugs

Table 1: Summary of Factors, Methods & Results

Factor Source/Method Result

Temperature (oC) Processed MWRA Data

Min-Max (Mean) *Upstream: 0.58 - 25.39 (12.63)

Middle: 8.44 - 22.25 (16.24) Mouth: 3.53-20.89 (13.81)

Salinity (PSU) Processed MWRA Data

Min-Max (Mean) Upstream: 0.24 - 31.15 (25.55) Middle: 0.24 - 32.97 (26.91)

Mouth: 0.19 - 31.18 (24.24)

Dissolved Oxygen (mg/L) Processed MWRA Data

Min-Max (Mean) Upstream: 5.75 - 9.95 (7.45) Middle: 6.35 - 9.04 (7.76)

Mouth: 7.58 - 10.42 (8.73)

pH Processed MWRA Data

Min-Max (Mean) Upstream: 7.21 - 7.95 (7.74)

Middle: 7.29 - 7.96 (7.77) Mouth: 7.13 - 8.00 (7.76)

Turbidity (NTU) Processed MWRA Data

Min-Max (Mean) Upstream: 2.00 - 29.50 (11.51)

Middle: 2.40 - 29.85 (9.06) Mouth: 2.15 - 28.60(7.96)

Nitrogen ELM Model Net DIN: 666413.3 kg N per yr

Substrate Personal observation in class survey of the estuary Primarily mud

Flow Rate Lynn's AP1 (Breault 2002) 0.6 to 3.1 m3/s

Wave Action Literature (Rana 2007; seagrassli.org) Wave action may be negligible for eelgrass growth in Neponset

Light IntensityCalculated using Secchi data and Beers-Lambert equation (Id = I0e-kd)

Light Intensity at bottom may be insufficient to support eelgrass growth

Grazers Review of published and grey Literature Mute swans, Brant geese, chink snails, marsh and blue crabs are potential grazers in the Neponset

Inhibitors Processed MWRA Data (Chl a) Min-Max (Mean) (µg/L) ** Mouth: 0.22 - 12.4 (3.166)

*Upstream: site 055; Middle: sites 054, 042; Mouth: sites 039, 040, 041, 084, 089, 140 **Mouth: site 140