New metrics - Chesapeake Bay #136

General statement of metrics or index needed
New metrics for Chesapeake Bay (Llanso and Dauer 2002) (revision of Weisberg 1997).

Community
Benthic macroinvertebrates (bugs)

Metric Names
FFG2 Deep Deposit (DD)
Taxa of Concern (pollution indicative taxa)
abundance (number per square meter)

nt_ffg2_dd, pi_ffg2_dd, pt_ffg2_dd
nt_toc, pi_toc, pt_toc
ni_m2

Scoring, Metrics
Include any special conditions for metric scoring.
For example, adjustments for drainage area need the formula and the field name.

Index
Include prefered name and class names.

Scoring, Index
Include criteria for index scoring

References
Llanso and Dauer 2002
https://eyesonthebay.dnr.maryland.gov/eyesonthebay/documents/benthic/[LTB2025Level_I_ReportVolume1.pdf](https://eyesonthebay.dnr.maryland.gov/eyesonthebay/documents/benthic/LTB2025Level_I_ReportVolume1.pdf)

Notes
Include any special exceptions or anything non-standard that should be considered in the calculations.